Bomb Smasher

Developer(s): M. Hampson
Date: 198x
Type: Cassette
Platform(s): TS 1000
Tags: Game

Bomb Smasher is a vertically scrolling shooter in which the player launches a projectile upward from a fixed horizontal position to destroy randomly placed bomb targets. The program uses a machine code routine embedded in the REM statement at line 1, called via RAND USR 16514, to handle movement or display logic outside of BASIC’s speed constraints. Target bombs are scattered across the screen using RND at program start, rendered as inverse-video asterisk characters. The player fires by pressing any key, and the shot travels upward one row per loop iteration; collision is detected by PEEKing the display file address to check for a non-space character at the projectile’s current position.

Program Analysis

Program Structure

The program is organized into several logical blocks:

  • Lines 1–32: Machine code storage, screen initialization, and random bomb placement.
  • Lines 40–50: Variable initialization (B = bullet active flag, S = score).
  • Lines 100–190: Main game loop — moves the bullet, checks collision, redraws.
  • Lines 200–230: Wait for keypress, launch bullet from row 22.
  • Lines 300–330: Game over screen, waits for SPACE (CHR$ 118), then restarts.
  • Lines 400–420: Score increment, bullet reset on hit.

Machine Code Routine

The REM statement at line 1 contains 31 bytes of Z80 machine code. It is invoked at line 110 with RAND USR 16514. The address 16514 corresponds to the start of the program in RAM (16509 for the system variable area start + a small offset into the REM data). Disassembling the bytes:

  • Bomb Smasher

    Developer(s): M. Hampson
    Date: 198x
    Type: Cassette
    Platform(s): TS 1000
    Tags: Game

    Bomb Smasher is a vertically scrolling shooter in which the player launches a projectile upward from a fixed horizontal position to destroy randomly placed bomb targets. The program uses a machine code routine embedded in the REM statement at line 1, called via RAND USR 16514, to handle movement or display logic outside of BASIC’s speed constraints. Target bombs are scattered across the screen using RND at program start, rendered as inverse-video asterisk characters. The player fires by pressing any key, and the shot travels upward one row per loop iteration; collision is detected by PEEKing the display file address to check for a non-space character at the projectile’s current position.

    Program Analysis

    Program Structure

    The program is organized into several logical blocks:

    • Lines 1–32: Machine code storage, screen initialization, and random bomb placement.
    • Lines 40–50: Variable initialization (B = bullet active flag, S = score).
    • Lines 100–190: Main game loop — moves the bullet, checks collision, redraws.
    • Lines 200–230: Wait for keypress, launch bullet from row 22.
    • Lines 300–330: Game over screen, waits for SPACE (CHR$ 118), then restarts.
    • Lines 400–420: Score increment, bullet reset on hit.

    Machine Code Routine

    The REM statement at line 1 contains 31 bytes of Z80 machine code. It is invoked at line 110 with RAND USR 16514. The address 16514 corresponds to the start of the program in RAM (16509 for the system variable area start + a small offset into the REM data). Disassembling the bytes:

    • \2A\0C\40 — LD HL,(400Ch): loads a display-related address.
    • \06\18 — LD B,24: sets a counter for 24 rows.
    • \C5 — PUSH BC
    • \23\7E\32\21\40 — increments HL, loads A from (HL), stores it to a fixed address.
    • \5D\23\01\1F\00\ED\B0 — uses LDIR to copy 31 bytes, implementing a scroll or display-copy operation.
    • \2B\3A\21\40\77\23\C1\10\E9 — loop back with DJNZ, effectively scrolling or shifting screen rows.
    • \C9 — RET

    This routine most likely implements a one-row upward scroll of a portion of the display file, giving the visual effect of the bullet moving smoothly through the playfield without slow BASIC redraw overhead.

    Collision Detection

    Collision is detected at lines 150–170 using a direct display file PEEK. The system variables at addresses 16398 and 16399 hold the low and high bytes of the display file address (D_FILE). The code computes the character at the current bullet row and column 16 by reading PEEK(PEEK 16398 + 256*PEEK 16399). A returned value of 8 (line 160) represents a newline character, indicating the bullet has gone off the top of the screen, triggering GAME OVER. Any other non-zero value (line 170) indicates a bomb character was hit, branching to the score routine at line 400.

    Screen Setup and Bomb Placement

    Line 20 fills the top portion of the screen with inverse space characters (\@@) to create a border or sky effect, then places an inverse-video paddle/base graphic at row 15. Lines 30–32 scatter 50 bomb markers (rendered as inverse * characters, i.e., %*) at random positions in rows 3–12 using INT(RND*10)+3 and INT(RND*32).

    Game Loop and Bullet Mechanics

    The main loop (lines 100–190) is entered repeatedly. The bullet position is tracked in variable P, and B is a Boolean flag (0 = no bullet, 1 = bullet active). Each iteration, P is decremented by 1 (line 135), moving the bullet up one row. The bullet is drawn at AT P,16 (line 140/155) and erased at line 180. If no bullet is active, the loop waits at line 200 for any keypress before launching from row 22.

    Key Variables

    VariablePurpose
    BBullet active flag (0 = none, 1 = in flight)
    PCurrent bullet row position
    SPlayer score (bombs destroyed)
    ZLoop counter for bomb placement
    NDisplay file character at bullet position

    Notable Techniques and Anomalies

    • POKE 16418,0 at line 10 clears the scroll counter (CDFLAG or similar system variable), suppressing the “scroll?” prompt.
    • The game over handler at line 310 waits for CHR$ 118, which is the ENTER key on the ZX81 keyboard, before restarting.
    • The bullet is always fired from column 16, so the entire game is a single vertical track — there is no horizontal movement of the player or the shot.
    • Because bombs are placed randomly at startup and never regenerated until RUN restarts the program, a full playthrough ends only when the bullet exits the top of the screen or a full restart is triggered.
    • The RAND USR call at line 110 inside the main loop means the machine code runs on every iteration, suggesting it performs per-frame display work rather than a one-time setup.

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    Source Code

       1 REM \2A\0C\40\06\18\C5\23\7E\32\21\40\54\5D\23\01\1F\00\ED\B0\2B\3A\21\40\77\23\C1\10\E9\C9\25\1C\1D
  10 POKE 16418,0
  20 PRINT "\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@";AT 15,5;"%            "
  30 FOR Z=1 TO 50
  31 PRINT AT INT (RND*10)+3,INT (RND*32);"%*"
  32 NEXT Z
  40 LET B=0
  50 LET S=0
 100 PRINT AT 22,15;"   "
 110 RAND USR 16514
 120 PRINT AT 22,15;"\..% \.."
 130 IF NOT B THEN GOTO 200
 135 LET P=P-1
 140 PRINT AT P,16;
 150 LET N=PEEK (PEEK 16398+256*PEEK 16399)
 155 PRINT "*"
 160 IF N=8 THEN GOTO 300
 170 IF N THEN GOTO 400
 180 PRINT AT P,16;" "
 190 GOTO 100
 200 IF INKEY$="" THEN GOTO 100
 210 LET P=22
 220 LET B=1
 230 GOTO 100
 300 PRINT AT 1,1;"GAME OVER...YOUR SCORE->";S
 310 IF INKEY$<>CHR$ 118 THEN GOTO 310
 320 CLS 
 330 RUN 
 400 LET S=S+1
 410 LET B=0
 420 GOTO 180

    Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.

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    A

    Bomb Smasher

    Developer(s): M. Hampson
    Date: 198x
    Type: Cassette
    Platform(s): TS 1000
    Tags: Game

    Bomb Smasher is a vertically scrolling shooter in which the player launches a projectile upward from a fixed horizontal position to destroy randomly placed bomb targets. The program uses a machine code routine embedded in the REM statement at line 1, called via RAND USR 16514, to handle movement or display logic outside of BASIC’s speed constraints. Target bombs are scattered across the screen using RND at program start, rendered as inverse-video asterisk characters. The player fires by pressing any key, and the shot travels upward one row per loop iteration; collision is detected by PEEKing the display file address to check for a non-space character at the projectile’s current position.

    Program Analysis

    Program Structure

    The program is organized into several logical blocks:

    • Lines 1–32: Machine code storage, screen initialization, and random bomb placement.
    • Lines 40–50: Variable initialization (B = bullet active flag, S = score).
    • Lines 100–190: Main game loop — moves the bullet, checks collision, redraws.
    • Lines 200–230: Wait for keypress, launch bullet from row 22.
    • Lines 300–330: Game over screen, waits for SPACE (CHR$ 118), then restarts.
    • Lines 400–420: Score increment, bullet reset on hit.

    Machine Code Routine

    The REM statement at line 1 contains 31 bytes of Z80 machine code. It is invoked at line 110 with RAND USR 16514. The address 16514 corresponds to the start of the program in RAM (16509 for the system variable area start + a small offset into the REM data). Disassembling the bytes:

    • \2A\0C\40 — LD HL,(400Ch): loads a display-related address.
    • \06\18 — LD B,24: sets a counter for 24 rows.
    • \C5 — PUSH BC
    • \23\7E\32\21\40 — increments HL, loads A from (HL), stores it to a fixed address.
    • \5D\23\01\1F\00\ED\B0 — uses LDIR to copy 31 bytes, implementing a scroll or display-copy operation.
    • \2B\3A\21\40\77\23\C1\10\E9 — loop back with DJNZ, effectively scrolling or shifting screen rows.
    • \C9 — RET

    This routine most likely implements a one-row upward scroll of a portion of the display file, giving the visual effect of the bullet moving smoothly through the playfield without slow BASIC redraw overhead.

    Collision Detection

    Collision is detected at lines 150–170 using a direct display file PEEK. The system variables at addresses 16398 and 16399 hold the low and high bytes of the display file address (D_FILE). The code computes the character at the current bullet row and column 16 by reading PEEK(PEEK 16398 + 256*PEEK 16399). A returned value of 8 (line 160) represents a newline character, indicating the bullet has gone off the top of the screen, triggering GAME OVER. Any other non-zero value (line 170) indicates a bomb character was hit, branching to the score routine at line 400.

    Screen Setup and Bomb Placement

    Line 20 fills the top portion of the screen with inverse space characters (\@@) to create a border or sky effect, then places an inverse-video paddle/base graphic at row 15. Lines 30–32 scatter 50 bomb markers (rendered as inverse * characters, i.e., %*) at random positions in rows 3–12 using INT(RND*10)+3 and INT(RND*32).

    Game Loop and Bullet Mechanics

    The main loop (lines 100–190) is entered repeatedly. The bullet position is tracked in variable P, and B is a Boolean flag (0 = no bullet, 1 = bullet active). Each iteration, P is decremented by 1 (line 135), moving the bullet up one row. The bullet is drawn at AT P,16 (line 140/155) and erased at line 180. If no bullet is active, the loop waits at line 200 for any keypress before launching from row 22.

    Key Variables

    VariablePurpose
    BBullet active flag (0 = none, 1 = in flight)
    PCurrent bullet row position
    SPlayer score (bombs destroyed)
    ZLoop counter for bomb placement
    NDisplay file character at bullet position

    Notable Techniques and Anomalies

    • POKE 16418,0 at line 10 clears the scroll counter (CDFLAG or similar system variable), suppressing the “scroll?” prompt.
    • The game over handler at line 310 waits for CHR$ 118, which is the ENTER key on the ZX81 keyboard, before restarting.
    • The bullet is always fired from column 16, so the entire game is a single vertical track — there is no horizontal movement of the player or the shot.
    • Because bombs are placed randomly at startup and never regenerated until RUN restarts the program, a full playthrough ends only when the bullet exits the top of the screen or a full restart is triggered.
    • The RAND USR call at line 110 inside the main loop means the machine code runs on every iteration, suggesting it performs per-frame display work rather than a one-time setup.

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    Source Code

       1 REM \2A\0C\40\06\18\C5\23\7E\32\21\40\54\5D\23\01\1F\00\ED\B0\2B\3A\21\40\77\23\C1\10\E9\C9\25\1C\1D
  10 POKE 16418,0
  20 PRINT "\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@";AT 15,5;"%            "
  30 FOR Z=1 TO 50
  31 PRINT AT INT (RND*10)+3,INT (RND*32);"%*"
  32 NEXT Z
  40 LET B=0
  50 LET S=0
 100 PRINT AT 22,15;"   "
 110 RAND USR 16514
 120 PRINT AT 22,15;"\..% \.."
 130 IF NOT B THEN GOTO 200
 135 LET P=P-1
 140 PRINT AT P,16;
 150 LET N=PEEK (PEEK 16398+256*PEEK 16399)
 155 PRINT "*"
 160 IF N=8 THEN GOTO 300
 170 IF N THEN GOTO 400
 180 PRINT AT P,16;" "
 190 GOTO 100
 200 IF INKEY$="" THEN GOTO 100
 210 LET P=22
 220 LET B=1
 230 GOTO 100
 300 PRINT AT 1,1;"GAME OVER...YOUR SCORE->";S
 310 IF INKEY$<>CHR$ 118 THEN GOTO 310
 320 CLS 
 330 RUN 
 400 LET S=S+1
 410 LET B=0
 420 GOTO 180

    Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.

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    C     — LD HL,(400Ch): loads a display-related address.
  • — LD B,24: sets a counter for 24 rows.
  • \C5 — PUSH BC
  • E — increments HL, loads A from (HL), stores it to a fixed address.
  • D itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56513 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.7 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.5" itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56513 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.7 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.5"F

    Bomb Smasher

    Developer(s): M. Hampson
    Date: 198x
    Type: Cassette
    Platform(s): TS 1000
    Tags: Game

    Bomb Smasher is a vertically scrolling shooter in which the player launches a projectile upward from a fixed horizontal position to destroy randomly placed bomb targets. The program uses a machine code routine embedded in the REM statement at line 1, called via RAND USR 16514, to handle movement or display logic outside of BASIC’s speed constraints. Target bombs are scattered across the screen using RND at program start, rendered as inverse-video asterisk characters. The player fires by pressing any key, and the shot travels upward one row per loop iteration; collision is detected by PEEKing the display file address to check for a non-space character at the projectile’s current position.

    Program Analysis

    Program Structure

    The program is organized into several logical blocks:

    • Lines 1–32: Machine code storage, screen initialization, and random bomb placement.
    • Lines 40–50: Variable initialization (B = bullet active flag, S = score).
    • Lines 100–190: Main game loop — moves the bullet, checks collision, redraws.
    • Lines 200–230: Wait for keypress, launch bullet from row 22.
    • Lines 300–330: Game over screen, waits for SPACE (CHR$ 118), then restarts.
    • Lines 400–420: Score increment, bullet reset on hit.

    Machine Code Routine

    The REM statement at line 1 contains 31 bytes of Z80 machine code. It is invoked at line 110 with RAND USR 16514. The address 16514 corresponds to the start of the program in RAM (16509 for the system variable area start + a small offset into the REM data). Disassembling the bytes:

    • \2A\0C\40 — LD HL,(400Ch): loads a display-related address.
    • \06\18 — LD B,24: sets a counter for 24 rows.
    • \C5 — PUSH BC
    • \23\7E\32\21\40 — increments HL, loads A from (HL), stores it to a fixed address.
    • \5D\23\01\1F\00\ED\B0 — uses LDIR to copy 31 bytes, implementing a scroll or display-copy operation.
    • \2B\3A\21\40\77\23\C1\10\E9 — loop back with DJNZ, effectively scrolling or shifting screen rows.
    • \C9 — RET

    This routine most likely implements a one-row upward scroll of a portion of the display file, giving the visual effect of the bullet moving smoothly through the playfield without slow BASIC redraw overhead.

    Collision Detection

    Collision is detected at lines 150–170 using a direct display file PEEK. The system variables at addresses 16398 and 16399 hold the low and high bytes of the display file address (D_FILE). The code computes the character at the current bullet row and column 16 by reading PEEK(PEEK 16398 + 256*PEEK 16399). A returned value of 8 (line 160) represents a newline character, indicating the bullet has gone off the top of the screen, triggering GAME OVER. Any other non-zero value (line 170) indicates a bomb character was hit, branching to the score routine at line 400.

    Screen Setup and Bomb Placement

    Line 20 fills the top portion of the screen with inverse space characters (\@@) to create a border or sky effect, then places an inverse-video paddle/base graphic at row 15. Lines 30–32 scatter 50 bomb markers (rendered as inverse * characters, i.e., %*) at random positions in rows 3–12 using INT(RND*10)+3 and INT(RND*32).

    Game Loop and Bullet Mechanics

    The main loop (lines 100–190) is entered repeatedly. The bullet position is tracked in variable P, and B is a Boolean flag (0 = no bullet, 1 = bullet active). Each iteration, P is decremented by 1 (line 135), moving the bullet up one row. The bullet is drawn at AT P,16 (line 140/155) and erased at line 180. If no bullet is active, the loop waits at line 200 for any keypress before launching from row 22.

    Key Variables

    VariablePurpose
    BBullet active flag (0 = none, 1 = in flight)
    PCurrent bullet row position
    SPlayer score (bombs destroyed)
    ZLoop counter for bomb placement
    NDisplay file character at bullet position

    Notable Techniques and Anomalies

    • POKE 16418,0 at line 10 clears the scroll counter (CDFLAG or similar system variable), suppressing the “scroll?” prompt.
    • The game over handler at line 310 waits for CHR$ 118, which is the ENTER key on the ZX81 keyboard, before restarting.
    • The bullet is always fired from column 16, so the entire game is a single vertical track — there is no horizontal movement of the player or the shot.
    • Because bombs are placed randomly at startup and never regenerated until RUN restarts the program, a full playthrough ends only when the bullet exits the top of the screen or a full restart is triggered.
    • The RAND USR call at line 110 inside the main loop means the machine code runs on every iteration, suggesting it performs per-frame display work rather than a one-time setup.

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    Source Code

       1 REM \2A\0C\40\06\18\C5\23\7E\32\21\40\54\5D\23\01\1F\00\ED\B0\2B\3A\21\40\77\23\C1\10\E9\C9\25\1C\1D
  10 POKE 16418,0
  20 PRINT "\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@";AT 15,5;"%            "
  30 FOR Z=1 TO 50
  31 PRINT AT INT (RND*10)+3,INT (RND*32);"%*"
  32 NEXT Z
  40 LET B=0
  50 LET S=0
 100 PRINT AT 22,15;"   "
 110 RAND USR 16514
 120 PRINT AT 22,15;"\..% \.."
 130 IF NOT B THEN GOTO 200
 135 LET P=P-1
 140 PRINT AT P,16;
 150 LET N=PEEK (PEEK 16398+256*PEEK 16399)
 155 PRINT "*"
 160 IF N=8 THEN GOTO 300
 170 IF N THEN GOTO 400
 180 PRINT AT P,16;" "
 190 GOTO 100
 200 IF INKEY$="" THEN GOTO 100
 210 LET P=22
 220 LET B=1
 230 GOTO 100
 300 PRINT AT 1,1;"GAME OVER...YOUR SCORE->";S
 310 IF INKEY$<>CHR$ 118 THEN GOTO 310
 320 CLS 
 330 RUN 
 400 LET S=S+1
 410 LET B=0
 420 GOTO 180

    Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.

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    \ED\B0     — uses LDIR to copy 31 bytes, implementing a scroll or display-copy operation.

  • Bomb Smasher

    Developer(s): M. Hampson
    Date: 198x
    Type: Cassette
    Platform(s): TS 1000
    Tags: Game

    Bomb Smasher is a vertically scrolling shooter in which the player launches a projectile upward from a fixed horizontal position to destroy randomly placed bomb targets. The program uses a machine code routine embedded in the REM statement at line 1, called via RAND USR 16514, to handle movement or display logic outside of BASIC’s speed constraints. Target bombs are scattered across the screen using RND at program start, rendered as inverse-video asterisk characters. The player fires by pressing any key, and the shot travels upward one row per loop iteration; collision is detected by PEEKing the display file address to check for a non-space character at the projectile’s current position.

    Program Analysis

    Program Structure

    The program is organized into several logical blocks:

    • Lines 1–32: Machine code storage, screen initialization, and random bomb placement.
    • Lines 40–50: Variable initialization (B = bullet active flag, S = score).
    • Lines 100–190: Main game loop — moves the bullet, checks collision, redraws.
    • Lines 200–230: Wait for keypress, launch bullet from row 22.
    • Lines 300–330: Game over screen, waits for SPACE (CHR$ 118), then restarts.
    • Lines 400–420: Score increment, bullet reset on hit.

    Machine Code Routine

    The REM statement at line 1 contains 31 bytes of Z80 machine code. It is invoked at line 110 with RAND USR 16514. The address 16514 corresponds to the start of the program in RAM (16509 for the system variable area start + a small offset into the REM data). Disassembling the bytes:

    • \2A\0C\40 — LD HL,(400Ch): loads a display-related address.
    • \06\18 — LD B,24: sets a counter for 24 rows.
    • \C5 — PUSH BC
    • \23\7E\32\21\40 — increments HL, loads A from (HL), stores it to a fixed address.
    • \5D\23\01\1F\00\ED\B0 — uses LDIR to copy 31 bytes, implementing a scroll or display-copy operation.
    • \2B\3A\21\40\77\23\C1\10\E9 — loop back with DJNZ, effectively scrolling or shifting screen rows.
    • \C9 — RET

    This routine most likely implements a one-row upward scroll of a portion of the display file, giving the visual effect of the bullet moving smoothly through the playfield without slow BASIC redraw overhead.

    Collision Detection

    Collision is detected at lines 150–170 using a direct display file PEEK. The system variables at addresses 16398 and 16399 hold the low and high bytes of the display file address (D_FILE). The code computes the character at the current bullet row and column 16 by reading PEEK(PEEK 16398 + 256*PEEK 16399). A returned value of 8 (line 160) represents a newline character, indicating the bullet has gone off the top of the screen, triggering GAME OVER. Any other non-zero value (line 170) indicates a bomb character was hit, branching to the score routine at line 400.

    Screen Setup and Bomb Placement

    Line 20 fills the top portion of the screen with inverse space characters (\@@) to create a border or sky effect, then places an inverse-video paddle/base graphic at row 15. Lines 30–32 scatter 50 bomb markers (rendered as inverse * characters, i.e., %*) at random positions in rows 3–12 using INT(RND*10)+3 and INT(RND*32).

    Game Loop and Bullet Mechanics

    The main loop (lines 100–190) is entered repeatedly. The bullet position is tracked in variable P, and B is a Boolean flag (0 = no bullet, 1 = bullet active). Each iteration, P is decremented by 1 (line 135), moving the bullet up one row. The bullet is drawn at AT P,16 (line 140/155) and erased at line 180. If no bullet is active, the loop waits at line 200 for any keypress before launching from row 22.

    Key Variables

    VariablePurpose
    BBullet active flag (0 = none, 1 = in flight)
    PCurrent bullet row position
    SPlayer score (bombs destroyed)
    ZLoop counter for bomb placement
    NDisplay file character at bullet position

    Notable Techniques and Anomalies

    • POKE 16418,0 at line 10 clears the scroll counter (CDFLAG or similar system variable), suppressing the “scroll?” prompt.
    • The game over handler at line 310 waits for CHR$ 118, which is the ENTER key on the ZX81 keyboard, before restarting.
    • The bullet is always fired from column 16, so the entire game is a single vertical track — there is no horizontal movement of the player or the shot.
    • Because bombs are placed randomly at startup and never regenerated until RUN restarts the program, a full playthrough ends only when the bullet exits the top of the screen or a full restart is triggered.
    • The RAND USR call at line 110 inside the main loop means the machine code runs on every iteration, suggesting it performs per-frame display work rather than a one-time setup.

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    Image Gallery

    Source Code

       1 REM \2A\0C\40\06\18\C5\23\7E\32\21\40\54\5D\23\01\1F\00\ED\B0\2B\3A\21\40\77\23\C1\10\E9\C9\25\1C\1D
  10 POKE 16418,0
  20 PRINT "\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@";AT 15,5;"%            "
  30 FOR Z=1 TO 50
  31 PRINT AT INT (RND*10)+3,INT (RND*32);"%*"
  32 NEXT Z
  40 LET B=0
  50 LET S=0
 100 PRINT AT 22,15;"   "
 110 RAND USR 16514
 120 PRINT AT 22,15;"\..% \.."
 130 IF NOT B THEN GOTO 200
 135 LET P=P-1
 140 PRINT AT P,16;
 150 LET N=PEEK (PEEK 16398+256*PEEK 16399)
 155 PRINT "*"
 160 IF N=8 THEN GOTO 300
 170 IF N THEN GOTO 400
 180 PRINT AT P,16;" "
 190 GOTO 100
 200 IF INKEY$="" THEN GOTO 100
 210 LET P=22
 220 LET B=1
 230 GOTO 100
 300 PRINT AT 1,1;"GAME OVER...YOUR SCORE->";S
 310 IF INKEY$<>CHR$ 118 THEN GOTO 310
 320 CLS 
 330 RUN 
 400 LET S=S+1
 410 LET B=0
 420 GOTO 180

    Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.

    Tags

    Archived Media Downloadable TS 1000 Game

    People

    Scroll to Top
    BA\C1\E9     — loop back with DJNZ, effectively scrolling or shifting screen rows.
  • \C9 — RET

This routine most likely implements a one-row upward scroll of a portion of the display file, giving the visual effect of the bullet moving smoothly through the playfield without slow BASIC redraw overhead.

Collision Detection

Collision is detected at lines 150–170 using a direct display file PEEK. The system variables at addresses 16398 and 16399 hold the low and high bytes of the display file address (D_FILE). The code computes the character at the current bullet row and column 16 by reading PEEK(PEEK 16398 + 256*PEEK 16399). A returned value of 8 (line 160) represents a newline character, indicating the bullet has gone off the top of the screen, triggering GAME OVER. Any other non-zero value (line 170) indicates a bomb character was hit, branching to the score routine at line 400.

Screen Setup and Bomb Placement

Line 20 fills the top portion of the screen with inverse space characters (\@@) to create a border or sky effect, then places an inverse-video paddle/base graphic at row 15. Lines 30–32 scatter 50 bomb markers (rendered as inverse * characters, i.e., %*) at random positions in rows 3–12 using INT(RND*10)+3 and INT(RND*32).

Game Loop and Bullet Mechanics

The main loop (lines 100–190) is entered repeatedly. The bullet position is tracked in variable P, and B is a Boolean flag (0 = no bullet, 1 = bullet active). Each iteration, P is decremented by 1 (line 135), moving the bullet up one row. The bullet is drawn at AT P,16 (line 140/155) and erased at line 180. If no bullet is active, the loop waits at line 200 for any keypress before launching from row 22.

Key Variables

VariablePurpose
BBullet active flag (0 = none, 1 = in flight)
PCurrent bullet row position
SPlayer score (bombs destroyed)
ZLoop counter for bomb placement
NDisplay file character at bullet position

Notable Techniques and Anomalies

  • POKE 16418,0 at line 10 clears the scroll counter (CDFLAG or similar system variable), suppressing the “scroll?” prompt.
  • The game over handler at line 310 waits for CHR$ 118, which is the ENTER key on the ZX81 keyboard, before restarting.
  • The bullet is always fired from column 16, so the entire game is a single vertical track — there is no horizontal movement of the player or the shot.
  • Because bombs are placed randomly at startup and never regenerated until RUN restarts the program, a full playthrough ends only when the bullet exits the top of the screen or a full restart is triggered.
  • The RAND USR call at line 110 inside the main loop means the machine code runs on every iteration, suggesting it performs per-frame display work rather than a one-time setup.

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Source Code

   1 REM 





			
			

		

							

				
					

				

	


	


		
					

				




	
	



	
	
		


			
			
Bomb Smasher

			
		


	
	
	


							

				





Developer(s): M. Hampson


Date: 198x


Type: Cassette


Platform(s): TS 1000



Tags: Game



					

				
		

Bomb Smasher is a vertically scrolling shooter in which the player launches a projectile upward from a fixed horizontal position to destroy randomly placed bomb targets. The program uses a machine code routine embedded in the REM statement at line 1, called via RAND USR 16514, to handle movement or display logic outside of BASIC’s speed constraints. Target bombs are scattered across the screen using RND at program start, rendered as inverse-video asterisk characters. The player fires by pressing any key, and the shot travels upward one row per loop iteration; collision is detected by PEEKing the display file address to check for a non-space character at the projectile’s current position.










Program Analysis





Program Structure





The program is organized into several logical blocks:





    

  • Lines 1–32: Machine code storage, screen initialization, and random bomb placement.
    • 




  • Lines 40–50: Variable initialization (B = bullet active flag, S = score).
    • 




  • Lines 100–190: Main game loop — moves the bullet, checks collision, redraws.
    • 




  • Lines 200–230: Wait for keypress, launch bullet from row 22.
    • 




  • Lines 300–330: Game over screen, waits for SPACE (CHR$ 118), then restarts.
    • 




  • Lines 400–420: Score increment, bullet reset on hit.
    • 






Machine Code Routine





The REM statement at line 1 contains 31 bytes of Z80 machine code. It is invoked at line 110 with RAND USR 16514. The address 16514 corresponds to the start of the program in RAM (16509 for the system variable area start + a small offset into the REM data). Disassembling the bytes:





    

  • \2A\0C\40 — LD HL,(400Ch): loads a display-related address.
    • 




  • \06\18 — LD B,24: sets a counter for 24 rows.
    • 




  • \C5 — PUSH BC
    • 




  • \23\7E\32\21\40 — increments HL, loads A from (HL), stores it to a fixed address.
    • 




  • \5D\23\01\1F\00\ED\B0 — uses LDIR to copy 31 bytes, implementing a scroll or display-copy operation.
    • 




  • \2B\3A\21\40\77\23\C1\10\E9 — loop back with DJNZ, effectively scrolling or shifting screen rows.
    • 




  • \C9 — RET
    • 






This routine most likely implements a one-row upward scroll of a portion of the display file, giving the visual effect of the bullet moving smoothly through the playfield without slow BASIC redraw overhead.





Collision Detection





Collision is detected at lines 150–170 using a direct display file PEEK. The system variables at addresses 16398 and 16399 hold the low and high bytes of the display file address (D_FILE). The code computes the character at the current bullet row and column 16 by reading PEEK(PEEK 16398 + 256*PEEK 16399). A returned value of 8 (line 160) represents a newline character, indicating the bullet has gone off the top of the screen, triggering GAME OVER. Any other non-zero value (line 170) indicates a bomb character was hit, branching to the score routine at line 400.





Screen Setup and Bomb Placement





Line 20 fills the top portion of the screen with inverse space characters (\@@) to create a border or sky effect, then places an inverse-video paddle/base graphic at row 15. Lines 30–32 scatter 50 bomb markers (rendered as inverse * characters, i.e., %*) at random positions in rows 3–12 using INT(RND*10)+3 and INT(RND*32).





Game Loop and Bullet Mechanics





The main loop (lines 100–190) is entered repeatedly. The bullet position is tracked in variable P, and B is a Boolean flag (0 = no bullet, 1 = bullet active). Each iteration, P is decremented by 1 (line 135), moving the bullet up one row. The bullet is drawn at AT P,16 (line 140/155) and erased at line 180. If no bullet is active, the loop waits at line 200 for any keypress before launching from row 22.





Key Variables





VariablePurpose
BBullet active flag (0 = none, 1 = in flight)
PCurrent bullet row position
SPlayer score (bombs destroyed)
ZLoop counter for bomb placement
NDisplay file character at bullet position





Notable Techniques and Anomalies





    

  • POKE 16418,0 at line 10 clears the scroll counter (CDFLAG or similar system variable), suppressing the “scroll?” prompt.
    • 




  • The game over handler at line 310 waits for CHR$ 118, which is the ENTER key on the ZX81 keyboard, before restarting.
    • 




  • The bullet is always fired from column 16, so the entire game is a single vertical track — there is no horizontal movement of the player or the shot.
    • 




  • Because bombs are placed randomly at startup and never regenerated until RUN restarts the program, a full playthrough ends only when the bullet exits the top of the screen or a full restart is triggered.
    • 




  • The RAND USR call at line 110 inside the main loop means the machine code runs on every iteration, suggesting it performs per-frame display work rather than a one-time setup.
    • 



		
							

				












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Source Code





   1 REM \2A\0C\40\06\18\C5\23\7E\32\21\40\54\5D\23\01\1F\00\ED\B0\2B\3A\21\40\77\23\C1\10\E9\C9\25\1C\1D
  10 POKE 16418,0
  20 PRINT "\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@";AT 15,5;"%            "
  30 FOR Z=1 TO 50
  31 PRINT AT INT (RND*10)+3,INT (RND*32);"%*"
  32 NEXT Z
  40 LET B=0
  50 LET S=0
 100 PRINT AT 22,15;"   "
 110 RAND USR 16514
 120 PRINT AT 22,15;"\..% \.."
 130 IF NOT B THEN GOTO 200
 135 LET P=P-1
 140 PRINT AT P,16;
 150 LET N=PEEK (PEEK 16398+256*PEEK 16399)
 155 PRINT "*"
 160 IF N=8 THEN GOTO 300
 170 IF N THEN GOTO 400
 180 PRINT AT P,16;" "
 190 GOTO 100
 200 IF INKEY$="" THEN GOTO 100
 210 LET P=22
 220 LET B=1
 230 GOTO 100
 300 PRINT AT 1,1;"GAME OVER...YOUR SCORE->";S
 310 IF INKEY$<>CHR$ 118 THEN GOTO 310
 320 CLS 
 330 RUN 
 400 LET S=S+1
 410 LET B=0
 420 GOTO 180









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Bomb Smasher

			
		


	
	
	


							

				





Developer(s): M. Hampson


Date: 198x


Type: Cassette


Platform(s): TS 1000



Tags: Game



					

				
		

Bomb Smasher is a vertically scrolling shooter in which the player launches a projectile upward from a fixed horizontal position to destroy randomly placed bomb targets. The program uses a machine code routine embedded in the REM statement at line 1, called via RAND USR 16514, to handle movement or display logic outside of BASIC’s speed constraints. Target bombs are scattered across the screen using RND at program start, rendered as inverse-video asterisk characters. The player fires by pressing any key, and the shot travels upward one row per loop iteration; collision is detected by PEEKing the display file address to check for a non-space character at the projectile’s current position.










Program Analysis





Program Structure





The program is organized into several logical blocks:





    

  • Lines 1–32: Machine code storage, screen initialization, and random bomb placement.
    • 




  • Lines 40–50: Variable initialization (B = bullet active flag, S = score).
    • 




  • Lines 100–190: Main game loop — moves the bullet, checks collision, redraws.
    • 




  • Lines 200–230: Wait for keypress, launch bullet from row 22.
    • 




  • Lines 300–330: Game over screen, waits for SPACE (CHR$ 118), then restarts.
    • 




  • Lines 400–420: Score increment, bullet reset on hit.
    • 






Machine Code Routine





The REM statement at line 1 contains 31 bytes of Z80 machine code. It is invoked at line 110 with RAND USR 16514. The address 16514 corresponds to the start of the program in RAM (16509 for the system variable area start + a small offset into the REM data). Disassembling the bytes:





    

  • \2A\0C\40 — LD HL,(400Ch): loads a display-related address.
    • 




  • \06\18 — LD B,24: sets a counter for 24 rows.
    • 




  • \C5 — PUSH BC
    • 




  • \23\7E\32\21\40 — increments HL, loads A from (HL), stores it to a fixed address.
    • 




  • \5D\23\01\1F\00\ED\B0 — uses LDIR to copy 31 bytes, implementing a scroll or display-copy operation.
    • 




  • \2B\3A\21\40\77\23\C1\10\E9 — loop back with DJNZ, effectively scrolling or shifting screen rows.
    • 




  • \C9 — RET
    • 






This routine most likely implements a one-row upward scroll of a portion of the display file, giving the visual effect of the bullet moving smoothly through the playfield without slow BASIC redraw overhead.





Collision Detection





Collision is detected at lines 150–170 using a direct display file PEEK. The system variables at addresses 16398 and 16399 hold the low and high bytes of the display file address (D_FILE). The code computes the character at the current bullet row and column 16 by reading PEEK(PEEK 16398 + 256*PEEK 16399). A returned value of 8 (line 160) represents a newline character, indicating the bullet has gone off the top of the screen, triggering GAME OVER. Any other non-zero value (line 170) indicates a bomb character was hit, branching to the score routine at line 400.





Screen Setup and Bomb Placement





Line 20 fills the top portion of the screen with inverse space characters (\@@) to create a border or sky effect, then places an inverse-video paddle/base graphic at row 15. Lines 30–32 scatter 50 bomb markers (rendered as inverse * characters, i.e., %*) at random positions in rows 3–12 using INT(RND*10)+3 and INT(RND*32).





Game Loop and Bullet Mechanics





The main loop (lines 100–190) is entered repeatedly. The bullet position is tracked in variable P, and B is a Boolean flag (0 = no bullet, 1 = bullet active). Each iteration, P is decremented by 1 (line 135), moving the bullet up one row. The bullet is drawn at AT P,16 (line 140/155) and erased at line 180. If no bullet is active, the loop waits at line 200 for any keypress before launching from row 22.





Key Variables





VariablePurpose
BBullet active flag (0 = none, 1 = in flight)
PCurrent bullet row position
SPlayer score (bombs destroyed)
ZLoop counter for bomb placement
NDisplay file character at bullet position





Notable Techniques and Anomalies





    

  • POKE 16418,0 at line 10 clears the scroll counter (CDFLAG or similar system variable), suppressing the “scroll?” prompt.
    • 




  • The game over handler at line 310 waits for CHR$ 118, which is the ENTER key on the ZX81 keyboard, before restarting.
    • 




  • The bullet is always fired from column 16, so the entire game is a single vertical track — there is no horizontal movement of the player or the shot.
    • 




  • Because bombs are placed randomly at startup and never regenerated until RUN restarts the program, a full playthrough ends only when the bullet exits the top of the screen or a full restart is triggered.
    • 




  • The RAND USR call at line 110 inside the main loop means the machine code runs on every iteration, suggesting it performs per-frame display work rather than a one-time setup.
    • 



		
							

				












Content















Appears On















Related Products















Related Articles















Related Content















Image Gallery






  
    
    










Source Code





   1 REM \2A\0C\40\06\18\C5\23\7E\32\21\40\54\5D\23\01\1F\00\ED\B0\2B\3A\21\40\77\23\C1\10\E9\C9\25\1C\1D
  10 POKE 16418,0
  20 PRINT "\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@";AT 15,5;"%            "
  30 FOR Z=1 TO 50
  31 PRINT AT INT (RND*10)+3,INT (RND*32);"%*"
  32 NEXT Z
  40 LET B=0
  50 LET S=0
 100 PRINT AT 22,15;"   "
 110 RAND USR 16514
 120 PRINT AT 22,15;"\..% \.."
 130 IF NOT B THEN GOTO 200
 135 LET P=P-1
 140 PRINT AT P,16;
 150 LET N=PEEK (PEEK 16398+256*PEEK 16399)
 155 PRINT "*"
 160 IF N=8 THEN GOTO 300
 170 IF N THEN GOTO 400
 180 PRINT AT P,16;" "
 190 GOTO 100
 200 IF INKEY$="" THEN GOTO 100
 210 LET P=22
 220 LET B=1
 230 GOTO 100
 300 PRINT AT 1,1;"GAME OVER...YOUR SCORE->";S
 310 IF INKEY$<>CHR$ 118 THEN GOTO 310
 320 CLS 
 330 RUN 
 400 LET S=S+1
 410 LET B=0
 420 GOTO 180









Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.





					

				
			




						

				







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	C\C5ED itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56513 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.7 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.5" itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56513 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.7 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.5"F





			
			

		

							

				
					

				

	


	


		
					

				




	
	



	
	
		


			
			
Bomb Smasher

			
		


	
	
	


							

				





Developer(s): M. Hampson


Date: 198x


Type: Cassette


Platform(s): TS 1000



Tags: Game



					

				
		

Bomb Smasher is a vertically scrolling shooter in which the player launches a projectile upward from a fixed horizontal position to destroy randomly placed bomb targets. The program uses a machine code routine embedded in the REM statement at line 1, called via RAND USR 16514, to handle movement or display logic outside of BASIC’s speed constraints. Target bombs are scattered across the screen using RND at program start, rendered as inverse-video asterisk characters. The player fires by pressing any key, and the shot travels upward one row per loop iteration; collision is detected by PEEKing the display file address to check for a non-space character at the projectile’s current position.










Program Analysis





Program Structure





The program is organized into several logical blocks:





    

  • Lines 1–32: Machine code storage, screen initialization, and random bomb placement.
    • 




  • Lines 40–50: Variable initialization (B = bullet active flag, S = score).
    • 




  • Lines 100–190: Main game loop — moves the bullet, checks collision, redraws.
    • 




  • Lines 200–230: Wait for keypress, launch bullet from row 22.
    • 




  • Lines 300–330: Game over screen, waits for SPACE (CHR$ 118), then restarts.
    • 




  • Lines 400–420: Score increment, bullet reset on hit.
    • 






Machine Code Routine





The REM statement at line 1 contains 31 bytes of Z80 machine code. It is invoked at line 110 with RAND USR 16514. The address 16514 corresponds to the start of the program in RAM (16509 for the system variable area start + a small offset into the REM data). Disassembling the bytes:





    

  • \2A\0C\40 — LD HL,(400Ch): loads a display-related address.
    • 




  • \06\18 — LD B,24: sets a counter for 24 rows.
    • 




  • \C5 — PUSH BC
    • 




  • \23\7E\32\21\40 — increments HL, loads A from (HL), stores it to a fixed address.
    • 




  • \5D\23\01\1F\00\ED\B0 — uses LDIR to copy 31 bytes, implementing a scroll or display-copy operation.
    • 




  • \2B\3A\21\40\77\23\C1\10\E9 — loop back with DJNZ, effectively scrolling or shifting screen rows.
    • 




  • \C9 — RET
    • 






This routine most likely implements a one-row upward scroll of a portion of the display file, giving the visual effect of the bullet moving smoothly through the playfield without slow BASIC redraw overhead.





Collision Detection





Collision is detected at lines 150–170 using a direct display file PEEK. The system variables at addresses 16398 and 16399 hold the low and high bytes of the display file address (D_FILE). The code computes the character at the current bullet row and column 16 by reading PEEK(PEEK 16398 + 256*PEEK 16399). A returned value of 8 (line 160) represents a newline character, indicating the bullet has gone off the top of the screen, triggering GAME OVER. Any other non-zero value (line 170) indicates a bomb character was hit, branching to the score routine at line 400.





Screen Setup and Bomb Placement





Line 20 fills the top portion of the screen with inverse space characters (\@@) to create a border or sky effect, then places an inverse-video paddle/base graphic at row 15. Lines 30–32 scatter 50 bomb markers (rendered as inverse * characters, i.e., %*) at random positions in rows 3–12 using INT(RND*10)+3 and INT(RND*32).





Game Loop and Bullet Mechanics





The main loop (lines 100–190) is entered repeatedly. The bullet position is tracked in variable P, and B is a Boolean flag (0 = no bullet, 1 = bullet active). Each iteration, P is decremented by 1 (line 135), moving the bullet up one row. The bullet is drawn at AT P,16 (line 140/155) and erased at line 180. If no bullet is active, the loop waits at line 200 for any keypress before launching from row 22.





Key Variables





VariablePurpose
BBullet active flag (0 = none, 1 = in flight)
PCurrent bullet row position
SPlayer score (bombs destroyed)
ZLoop counter for bomb placement
NDisplay file character at bullet position





Notable Techniques and Anomalies





    

  • POKE 16418,0 at line 10 clears the scroll counter (CDFLAG or similar system variable), suppressing the “scroll?” prompt.
    • 




  • The game over handler at line 310 waits for CHR$ 118, which is the ENTER key on the ZX81 keyboard, before restarting.
    • 




  • The bullet is always fired from column 16, so the entire game is a single vertical track — there is no horizontal movement of the player or the shot.
    • 




  • Because bombs are placed randomly at startup and never regenerated until RUN restarts the program, a full playthrough ends only when the bullet exits the top of the screen or a full restart is triggered.
    • 




  • The RAND USR call at line 110 inside the main loop means the machine code runs on every iteration, suggesting it performs per-frame display work rather than a one-time setup.
    • 



		
							

				












Content















Appears On















Related Products















Related Articles















Related Content















Image Gallery






  
    
    










Source Code





   1 REM \2A\0C\40\06\18\C5\23\7E\32\21\40\54\5D\23\01\1F\00\ED\B0\2B\3A\21\40\77\23\C1\10\E9\C9\25\1C\1D
  10 POKE 16418,0
  20 PRINT "\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@";AT 15,5;"%            "
  30 FOR Z=1 TO 50
  31 PRINT AT INT (RND*10)+3,INT (RND*32);"%*"
  32 NEXT Z
  40 LET B=0
  50 LET S=0
 100 PRINT AT 22,15;"   "
 110 RAND USR 16514
 120 PRINT AT 22,15;"\..% \.."
 130 IF NOT B THEN GOTO 200
 135 LET P=P-1
 140 PRINT AT P,16;
 150 LET N=PEEK (PEEK 16398+256*PEEK 16399)
 155 PRINT "*"
 160 IF N=8 THEN GOTO 300
 170 IF N THEN GOTO 400
 180 PRINT AT P,16;" "
 190 GOTO 100
 200 IF INKEY$="" THEN GOTO 100
 210 LET P=22
 220 LET B=1
 230 GOTO 100
 300 PRINT AT 1,1;"GAME OVER...YOUR SCORE->";S
 310 IF INKEY$<>CHR$ 118 THEN GOTO 310
 320 CLS 
 330 RUN 
 400 LET S=S+1
 410 LET B=0
 420 GOTO 180









Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.





					

				
			




						

				







Tags





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People







					

				



			

			
		
	



	
 
	


	












	
                
                	Scroll to Top


			
			













	\ED\B0





			
			

		

							

				
					

				

	


	


		
					

				




	
	



	
	
		


			
			
Bomb Smasher

			
		


	
	
	


							

				





Developer(s): M. Hampson


Date: 198x


Type: Cassette


Platform(s): TS 1000



Tags: Game



					

				
		

Bomb Smasher is a vertically scrolling shooter in which the player launches a projectile upward from a fixed horizontal position to destroy randomly placed bomb targets. The program uses a machine code routine embedded in the REM statement at line 1, called via RAND USR 16514, to handle movement or display logic outside of BASIC’s speed constraints. Target bombs are scattered across the screen using RND at program start, rendered as inverse-video asterisk characters. The player fires by pressing any key, and the shot travels upward one row per loop iteration; collision is detected by PEEKing the display file address to check for a non-space character at the projectile’s current position.










Program Analysis





Program Structure





The program is organized into several logical blocks:





    

  • Lines 1–32: Machine code storage, screen initialization, and random bomb placement.
    • 




  • Lines 40–50: Variable initialization (B = bullet active flag, S = score).
    • 




  • Lines 100–190: Main game loop — moves the bullet, checks collision, redraws.
    • 




  • Lines 200–230: Wait for keypress, launch bullet from row 22.
    • 




  • Lines 300–330: Game over screen, waits for SPACE (CHR$ 118), then restarts.
    • 




  • Lines 400–420: Score increment, bullet reset on hit.
    • 






Machine Code Routine





The REM statement at line 1 contains 31 bytes of Z80 machine code. It is invoked at line 110 with RAND USR 16514. The address 16514 corresponds to the start of the program in RAM (16509 for the system variable area start + a small offset into the REM data). Disassembling the bytes:





    

  • \2A\0C\40 — LD HL,(400Ch): loads a display-related address.
    • 




  • \06\18 — LD B,24: sets a counter for 24 rows.
    • 




  • \C5 — PUSH BC
    • 




  • \23\7E\32\21\40 — increments HL, loads A from (HL), stores it to a fixed address.
    • 




  • \5D\23\01\1F\00\ED\B0 — uses LDIR to copy 31 bytes, implementing a scroll or display-copy operation.
    • 




  • \2B\3A\21\40\77\23\C1\10\E9 — loop back with DJNZ, effectively scrolling or shifting screen rows.
    • 




  • \C9 — RET
    • 






This routine most likely implements a one-row upward scroll of a portion of the display file, giving the visual effect of the bullet moving smoothly through the playfield without slow BASIC redraw overhead.





Collision Detection





Collision is detected at lines 150–170 using a direct display file PEEK. The system variables at addresses 16398 and 16399 hold the low and high bytes of the display file address (D_FILE). The code computes the character at the current bullet row and column 16 by reading PEEK(PEEK 16398 + 256*PEEK 16399). A returned value of 8 (line 160) represents a newline character, indicating the bullet has gone off the top of the screen, triggering GAME OVER. Any other non-zero value (line 170) indicates a bomb character was hit, branching to the score routine at line 400.





Screen Setup and Bomb Placement





Line 20 fills the top portion of the screen with inverse space characters (\@@) to create a border or sky effect, then places an inverse-video paddle/base graphic at row 15. Lines 30–32 scatter 50 bomb markers (rendered as inverse * characters, i.e., %*) at random positions in rows 3–12 using INT(RND*10)+3 and INT(RND*32).





Game Loop and Bullet Mechanics





The main loop (lines 100–190) is entered repeatedly. The bullet position is tracked in variable P, and B is a Boolean flag (0 = no bullet, 1 = bullet active). Each iteration, P is decremented by 1 (line 135), moving the bullet up one row. The bullet is drawn at AT P,16 (line 140/155) and erased at line 180. If no bullet is active, the loop waits at line 200 for any keypress before launching from row 22.





Key Variables





VariablePurpose
BBullet active flag (0 = none, 1 = in flight)
PCurrent bullet row position
SPlayer score (bombs destroyed)
ZLoop counter for bomb placement
NDisplay file character at bullet position





Notable Techniques and Anomalies





    

  • POKE 16418,0 at line 10 clears the scroll counter (CDFLAG or similar system variable), suppressing the “scroll?” prompt.
    • 




  • The game over handler at line 310 waits for CHR$ 118, which is the ENTER key on the ZX81 keyboard, before restarting.
    • 




  • The bullet is always fired from column 16, so the entire game is a single vertical track — there is no horizontal movement of the player or the shot.
    • 




  • Because bombs are placed randomly at startup and never regenerated until RUN restarts the program, a full playthrough ends only when the bullet exits the top of the screen or a full restart is triggered.
    • 




  • The RAND USR call at line 110 inside the main loop means the machine code runs on every iteration, suggesting it performs per-frame display work rather than a one-time setup.
    • 



		
							

				












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   1 REM \2A\0C\40\06\18\C5\23\7E\32\21\40\54\5D\23\01\1F\00\ED\B0\2B\3A\21\40\77\23\C1\10\E9\C9\25\1C\1D
  10 POKE 16418,0
  20 PRINT "\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@";AT 15,5;"%            "
  30 FOR Z=1 TO 50
  31 PRINT AT INT (RND*10)+3,INT (RND*32);"%*"
  32 NEXT Z
  40 LET B=0
  50 LET S=0
 100 PRINT AT 22,15;"   "
 110 RAND USR 16514
 120 PRINT AT 22,15;"\..% \.."
 130 IF NOT B THEN GOTO 200
 135 LET P=P-1
 140 PRINT AT P,16;
 150 LET N=PEEK (PEEK 16398+256*PEEK 16399)
 155 PRINT "*"
 160 IF N=8 THEN GOTO 300
 170 IF N THEN GOTO 400
 180 PRINT AT P,16;" "
 190 GOTO 100
 200 IF INKEY$="" THEN GOTO 100
 210 LET P=22
 220 LET B=1
 230 GOTO 100
 300 PRINT AT 1,1;"GAME OVER...YOUR SCORE->";S
 310 IF INKEY$<>CHR$ 118 THEN GOTO 310
 320 CLS 
 330 RUN 
 400 LET S=S+1
 410 LET B=0
 420 GOTO 180









Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.





					

				
			




						

				







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	BA\C1\E9\C9 itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56513 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.7 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.5"C itemtype='https://schema.org/Blog' itemscope='itemscope' class="wp-singular computer_media-template-default single single-computer_media postid-56513 wp-custom-logo wp-embed-responsive wp-theme-astra wp-child-theme-astra-child ast-desktop ast-separate-container ast-left-sidebar astra-4.12.7 group-blog ast-blog-single-style-1 ast-custom-post-type ast-single-post ast-inherit-site-logo-transparent ast-hfb-header ast-full-width-primary-header ast-box-layout ast-normal-title-enabled astra-addon-4.12.5"D
  10 POKE 16418,0
  20 PRINT "\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@\@@";AT 15,5;"%            "
  30 FOR Z=1 TO 50
  31 PRINT AT INT (RND*10)+3,INT (RND*32);"%*"
  32 NEXT Z
  40 LET B=0
  50 LET S=0
 100 PRINT AT 22,15;"   "
 110 RAND USR 16514
 120 PRINT AT 22,15;"\..% \.."
 130 IF NOT B THEN GOTO 200
 135 LET P=P-1
 140 PRINT AT P,16;
 150 LET N=PEEK (PEEK 16398+256*PEEK 16399)
 155 PRINT "*"
 160 IF N=8 THEN GOTO 300
 170 IF N THEN GOTO 400
 180 PRINT AT P,16;" "
 190 GOTO 100
 200 IF INKEY$="" THEN GOTO 100
 210 LET P=22
 220 LET B=1
 230 GOTO 100
 300 PRINT AT 1,1;"GAME OVER...YOUR SCORE->";S
 310 IF INKEY$<>CHR$ 118 THEN GOTO 310
 320 CLS 
 330 RUN 
 400 LET S=S+1
 410 LET B=0
 420 GOTO 180

Note: Type-in program listings on this website use ZMAKEBAS notation for graphics characters.

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Archived Media Downloadable TS 1000 Game

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