Defend the Earth from the invading UFO’s in this ZX81 shooter.
PROG : 16509
D-FILE: 17429
VARS : 18222
E-LINE: 18364
STKBOT: 18364
STKEND: 18364
9999 means line number
PRINT means treat as KEYWORD P
1 REM **U.F.O**JLW/1984******
10 DIM C$(3)
20 CLS
30 PLOT 31,0
40 PLOT 32,0
50 PLOT 33,0
55 PLOT 32,1
60 LET E=20
70 LET B=0
75 LET F=32
80 FOR Z=1 TO 20
85 LET H=0
90 FOR X=0 TO 53 STEP 4
100 GOSUB 190
120 NEXT X
130 NEXT Z
140 PRINT "YOU HIT ";B;" OUT OF
";E;"."
150 PRINT "DO YOU WANT TO TRY A
GAIN? (Y/N)"
160 IF INKEY$="N" THEN STOP
170 IF INKEY$="Y" THEN GOTO 10
180 GOTO 160
190 FOR Y=2 TO 8
200 PLOT X+Y,43
210 NEXT Y
220 FOR W=0 TO 10
230 PLOT X+W,42
240 NEXT W
250 FOR V=0 TO 10 STEP 2
260 PLOT X+V,41
270 NEXT V
280 IF INKEY$<>"" THEN GOSUB 39
0
290 FOR Y=2 TO 8
300 UNPLOT X+Y,43
310 NEXT Y
320 FOR W=0 TO 10
330 UNPLOT X+W,42
340 NEXT W
350 FOR V=0 TO 10 STEP 2
360 UNPLOT X+V,41
370 NEXT V
380 RETURN
390 FOR J=2 TO 41
400 PLOT 32,J
410 UNPLOT 32,J
420 NEXT J
425 IF H=1 THEN GOTO 450
430 IF F>=X AND F<=X+10 THEN
LET B=B+1
440 IF F>=X AND F<=X+10 THEN
LET H=1
450 RETURN
500 SAVE "UFO"
510 RUN