---
title: "Comet Crusher"
id: 72851
type: "computer_media"
slug: "comet-crusher"
url: "http://localhost/computer_media/comet-crusher/"
markdown_url: "http://localhost/computer_media/comet-crusher.md"
published_at: "2026-10-27T15:54:37+00:00"
modified_at: "2026-10-27T15:54:37+00:00"
author: "David Anderson"
featured_image:
  url: "http://localhost/wp-content/uploads/2026/10/d-3.png"
excerpt: "Launch your rocket at the right moment to destroy a comet crossing the top of the screen."
post_tag:
  - name: "Downloadable"
    slug: "downloadable"
    taxonomy: "post_tag"
    url: "http://localhost/tag/downloadable/"
  - name: "TS 2068"
    slug: "ts2068"
    taxonomy: "post_tag"
    url: "http://localhost/tag/ts2068/"
model:
  - name: "Timex/Sinclair 2068"
    slug: "ts-2068"
    taxonomy: "model"
    url: "http://localhost/model/ts-2068/"
indiv:
  - name: "Chuck Dawson"
    slug: "chuck-dawson"
    taxonomy: "indiv"
    url: "http://localhost/indiv/chuck-dawson/"
genre:
  - name: "Arcade"
    slug: "arcade"
    taxonomy: "genre"
    url: "http://localhost/type/arcade/"
media_type: "Program"
programmers:
  - name: "Chuck Dawson"
    slug: "chuck-dawson"
    taxonomy: "indiv"
    url: "http://localhost/indiv/chuck-dawson/"
download_url: "https://archive.org/download/timex-sinclair-software-archive/Comet%20Crusher%20%281982%29%28Dawson%2C%20Chuck%29%28TS2068%29%28US%29%28Program%29.zip"
tsrun_member: "Comet Crusher (1982)(Dawson, Chuck)(TS2068)(US)(Program)/Comet Crusher (1982)(Dawson, Chuck)(TS2068)(US)(Program).tap"
mediadate: "1982"
images:
  - url: "http://localhost/wp-content/uploads/2026/10/d-3.png"
  - url: "http://localhost/wp-content/uploads/2026/10/e-1-1.png"
article_media:
  - id: 24353
    title: "Comet Crusher"
    type: "article"
    url: "http://localhost/article/comet-crusher/"
media_type_tags: "Arcade"
license: false
---

# Comet Crusher

A comet crawls across the top of the screen while your rocket waits on the launch pad. Press F to fire: the rocket climbs with a flame trail, and if it reaches the comet’s height as the comet passes overhead you score a hit. A miss resets the round.

The program is the type-in from SYNC v2 n4 (1982) (see the article Comet Crusher). Bob Swoger’s copy was transferred from the TS1000 to the TS2068 with Upload 2000.

## Program Analysis

The comet moves one ZX81 pixel per step with `PAUSE 45` between steps, and the rocket rises one line per step after launch. A hit is detected at line 150 when the comet’s x position is 39 and the rocket is in the top rows.

This copy came from a Larken disk. The ZX81 POKEs to its FRAMES counter were removed, the comet is drawn as a ZX81-sized pixel by a subroutine at 2010 (Upload 2000 had dropped `UNPLOT`), and F is accepted in lower case too. Tested in ZEsarUX on a stock TS2068.

## Source Code

```
    1 REM ::COMET::CRUSHER::TO::SAVE::GOTO::500.::
    5 CLS 
   10 LET H=18
   15 LET A=0
   20 LET Y=37
   25 LET X=0
   30 PRINT AT 18,19;":'";TAB 19;" :";TAB 19;".'. "
   40 PRINT AT 20,0;"::PRESS::'F'::TO::FIRE.::"
   50 PRINT AT 21,0;"::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::"
   60 LET u=X-1: LET v=Y: LET w=1: GO SUB 2010
   70 LET u=X: LET v=Y: LET w=0: GO SUB 2010
   80 LET X=X+1
   85 PAUSE 45
   87 REM  removed (LKDOS-only)
   90 IF X>63 THEN GO TO 1
  100 IF INKEY$="F" OR INKEY$="f" THEN LET A=1
  110 IF A=1 THEN PRINT AT 20,0;"                 "
  120 IF A=0 THEN GO TO 30
  130 LET H=H-1
  140 PRINT AT H,19;":'";TAB 19;" :";TAB 19;".'. ";TAB 19;"* ";TAB 19;"  "
  150 IF X=39 AND H<4 AND H>0 THEN GO TO 200
  160 IF H=0 THEN GO TO 1
  170 IF H=17 THEN GO TO 50
  180 GO TO 60
  200 CLS 
  210 PRINT AT 3,19;"::HIT::"
  220 PAUSE 500
  225 REM  removed (LKDOS-only)
  230 RUN 
  500 SAVE "COMET CRUSHER"
  510 RUN 
 2000 REM plot (w=0) or unplot (w=1) one ZX81-size pixel at u,v
 2010 FOR q=0 TO 3: PLOT INVERSE w;4*u,4*v+q: DRAW INVERSE w;3,0: NEXT q: RETURN 
 9992 SAVE "CMTCRH.B1"
 9998 REM  was LKDOS-only
```