Invaders
How could we write a bumper book of programs without including the classic Invaders game? Well, here it is, complete with shields and Mothership and a screen full of the dreaded Aliens.
10 REM INVADERS
20 REM @ MICHAEL BEWS
70 DIM 1(50)
40 MODE 1:BORDER 0:INK 0,0:INK 1,24:INK 2,20:INK 3,6:WINDOW #1,1,40,1,25:PAPER # 1,0:PEN #1,1:CLS #1
50 J$(1)=STRING$(32,32)
60 GOSUB 1350
70 XW=0:XV=0:YU=0:IMP=0:TC=0:RA=0:RR=80: HS=-100:TS=0:A=0:C=0:FX=0:L=0:P=7:0=6:T= 2:U=1:V=5:W=10:SC=0:XP=0:Z=1
80 YY=0:)(Z=2:XN=0:XS=0
90 GOSUB 1180:GOTO 720
100 REM MAIN PROGRAM LOOP
110 REM
120 REM INVADER SHUFFLE
130 REM
140 IF TC=U THEN TC=0: GOTO 630
150 FX=U: X=U
160 IF I(X+L*P)=0 THEN FX=0: GOTO 180 170 X=X+U: IF X<P+U THEN 160
leo PEN INT(2.5—Z/2): FW=U: X=U
190 IF I(X)=0 THEN FW=0: GOTO 210
200 X=X+U: IF X<50 THEN 190
210 IF FW=U THEN FW=0: GOTO 1070
220 IF FX=U THEN GOTO 330
230 IF FX=U THEN FX=0: GOTO 330
240 IF L+A>19 THEN GOTO 1050
250 LOCATE 1,L+A+1: IF (Z=—LJ AND TC=0) T HEN PRINT" ";
260 FOR X = U TO P: IF I(P*L+X)=U THEN P RINT"	"-- GOTO 280
270 PRINT 1$;
280 NEXT X
290 PEN 1