Invaders from Outer Space

1000 REM INVADERS FROM OUTER SPACE
1002 GRAPHICS 5
1004 POKE 53277,0
1006 POKE 752,1
1008 ?
1009 ? " INVADERS FROM OUTER SPACE"
1010 ? " (C) PRZEMYSLAW KOBYLANSKI 2024"
1020 GOSUB 7000:REM PANORAMA
1030 GOSUB 9000:REM BITMAPS
1040 GOSUB 8000:REM P/M GRAPHICS
1045 ENABLE=0
1047 VISIBLE=0
1050 REM MAIN LOOP
1060 GOSUB 2000:REM INVADERS
1070 GOSUB 3000:REM UFO
1080 GOTO 1050
2000 REM INVADERS
2010 FOR I=0 TO 2
2020 IF I>0 THEN 2070
2030 X1=X(0)+DX(0)
2040 IF X1<48 OR X1>X(1)-8 THEN DX(0)=-DX(0)
2050 X(0)=X(0)+DX(0)
2060 GOTO 2150
2070 IF I<2 THEN 2120
2080 X1=X(2)+DX(2)
2090 IF X1<X(1)+8 OR X1>200 THEN DX(2)=-DX(2)
2100 X(2)=X(2)+DX(2)
2110 GOTO 2150
2120 X1=X(I)+DX(I)
2130 IF X1<X(I-1)+8 OR X1>X(I+1)-8 THEN DX(I)=-DX(I)
2140 X(I)=X(I)+DX(I)
2150 NEXT I
2160 FOR I=0 TO 2
2170 MOD=X(I)-2*INT(X(I)/2)
2180 POKE 53248+I,X(I)
2190 FOR J=0 TO 7
2200 POKE PB(I)+64+J,BM(MOD,J)
2210 NEXT J
2220 NEXT I
2230 SOUND 0,150,15,100
2240 FOR D=1 TO 6
2250 NEXT D
2260 SOUND 0,0,0,0
2270 RETURN
3000 REM UFO
3010 IF ENABLE THEN 3050
3020 ENABLE=RND(1)<0.02
3030 IF NOT (ENABLE) THEN RETURN
3040 VISIBLE=0
3050 IF VISIBLE THEN 3130
3060 DX(3)=3-6*INT(2*RND(1))
3070 X(3)=32+176*(DX(3)<0)
3075 POKE 53251,X(3)
3080 FOR I=0 TO 7
3090 POKE PB(3)+15+I,BM(2,I)
3100 NEXT I
3110 VISIBLE=1
3115 SOUND 1,80,2,3
3120 RETURN
3130 X(3)=X(3)+DX(3)
3140 IF DX(3)>0 THEN 3220
3150 IF X(3)>31 THEN 3300
3160 FOR I=0 TO 7
3170 POKE PB(3)+15+I,0
3180 NEXT I
3190 VISIBLE=0
3200 0
3200 ENABLE=0
3205 SOUND 1,0,0,0
3210 RETURN
3220 IF X(3)<209 THEN 3300
3230 GOTO 3160
3300 POKE 53251,X(3)
3310 RETURN
7000 REM PANORAMA
7002 H1=0
7004 H2=10
7006 H3=20
7010 FOR X=0 TO 79
7020 COLOR 3
7030 PLOT X,H1
7040 DRAWTO X,47
7050 COLOR 2
7060 PLOT X,H2
7070 DRAWTO X,47
7080 COLOR 1
7090 PLOT X,H3
7100 DRAWTO X,47
7110 H=H1+1-2*INT(2*RND(1))
7120 IF H<0 OR H>23 THEN 7110
7125 H1=H
7130 H=H2+1-2*INT(2*RND(1))
7140 IF H<10 OR H>20 THEN 7130
7145 H2=H
7150 H=H3+1-2*INT(2*RND(1))
7160 IF H<15 OR H>20 THEN 7150
7165 H3=H
7170 NEXT X
7180 RETURN
8000 REM P/M GRAPHICS
8005 POKE 53277,0
8010 TOP=156
8020 POKE 106,TOP
8030 PB=TOP*256
8040 POKE 54279,TOP
8050 POKE 559,46:REM DOUBLE
8060 POKE 623,1:REM PRIORITY
8080 POKE 53256,0
8085 DIM X(3),PB(3),DX(3)
8090 FOR I=0 TO 3
8095 POKE 704+I,101+3*I:REM COLOR
8100 POKE 53256+I,0:REM NORMAL SIZE
8110 X(I)=48+I*38+INT(38*RND(1))
8115 DX(I)=1+2*I-(2+4*I)*INT(2*RND(1))
8120 POKE 53248+I,X(I)
8130 PB(I)=PB+512+I*128
8150 NEXT I
8155 POKE 53259,1:REM DOUBLE SIZE
8160 FOR A=PB(0) TO PB(0)+1023
8170 POKE A,0
8180 NEXT A
8190 FOR I=0 TO 2
8200 MOD=X(I)-2*INT(X(I)/2)
8210 FOR J=0 TO 7
8220 POKE PB(I)+64+J,BM(MOD,J)
8230 NEXT J
8240 NEXT I
8250 POKE 53277,3
8260 RETURN
9000 REM BITMAPS
9010 DIM BM(3,7)
9020 FOR I=0 TO 1
9030 FOR J=0 TO 7
9040 READ V
9050 BM(I,J)=V
9060 NEXT J
9070 NEXT I
9080 FOR J=0 TO 7
9090 READ V
9100 BM(2,J)=V
9110 NEXT J
9120 RETURN
9200 DATA 24,60,126,219,126,60,66,36
9210 DATA 24,60,126,219,126,24,36,66
9220 DATA 0,0,60,126,219,255,90,0