Petit Computer Journal #29

A Simple Sprite Game


I've always said that writing a computer program is pretty easy if you know what you're doing. The question is, how easy can it be? I've written a version of Snakes and Ladders game in under 10 minutes. How quickly and easily can I write a sprite based game? Certainly, not too difficult.

I'm curious as to just how easy it is to write one. Certainly, there is the control. I settled for Up-Down-Fire, which is a variation of Left-Right-Fire. I was hoping for a single screen challenge program, and I managed to do it. However, it isn't fun at all. Also, it turns out that I don't need the Up-Down movement at all. Just sit there and hit the fire button!

1. CLS:Y=0:A=256:C=128:S=0
2. SPSET 1,96,0,0,0,0:T=3600
3. SPSET 2,40,0,0,0,0
4. SPOFS 2,-16,0,0:SPANIM 2,2,15
5. SPSET 10,13,3,0,0,0
6. @LOOP
7. T=T-1:IF T<0 THEN END
8. VSYNC 1:B=BUTTON(0):DX=0:DY=0
9. LOCATE 0,0:?"S=";S,"T=";T;" "
10. IF SPHIT(10) THEN S=S+1:BEEP
11. IF !SPCHK(10) THEN GOSUB @MM
12. IF (B AND 16) THEN GOSUB @FR
13. IF !(B AND 3) GOTO @LOOP
14. DY=(B AND 3)*2-3
15. Y=Y+DY:IF Y<0 THEN Y=Y+192
16. Y=Y%192:SPOFS 1,0,Y,0
17. GOTO @LOOP
18. @FR
19. SPOFS 2,0,Y,0:SPOFS 2,A,Y,C/2
20. RETURN
21. @MM
22. SPOFS 10,99+RND(99),-20,0
23. SPOFS 10,99+RND(99),2*C,C
24. RETURN

It's all very well and good for a single screen challenge, but I was curious as to how much better it would be, had it been a better fleshed out game. So, forget about the single screen challenge and just do better!

1. CLS:Y=0:A=256:C=128:S=0
2. BGFILL 0,0,0,63,63,9,8,0,0
3. FOR I=1 TO 32
4. BGPUT 0,RND(64),RND(64),32,8,0,0
5. NEXT
6. SPSET 1,96,0,0,0,0
7. SPSET 2,40,0,0,0,0
8. SPOFS 2,-16,0,0:SPANIM 2,2,15
9. FOR I=10 TO 70
10. SPSET I,13,3,0,0,0
11. SPOFS I,99,-50,0
12. NEXT
13. @INIT
14. BGMPLAY 23
15. T=10800:S=0
16. @LOOP
17. IF HYC<S THEN HC=S
18. IF !BGCHK(0) THEN BGOFS 0,RND(512),RND(512),360
19. T=T-1:M=FLOOR(T/180):IF T<0 THEN GOTO @END
20. VSYNC 1:B=BUTTON(0):DX=0:DY=0
21. LOCATE 0,0:?"$=";S,"TIME=";M;"   ","HI $=";HC;"   "
22. FOR I=10 TO 70-M
23. IF SPHITSP(I,2) THEN S=S+1:BEEP 3:GOSUB @HIT
24. IF !SPCHK(I) THEN GOSUB @MM
25. NEXT
26. IF (B AND 16) THEN GOSUB @FR
27. IF !(B AND 3) GOTO @LOOP
28. DY=(B AND 3)*2-3
29. Y=Y+DY:IF Y<0 THEN Y=Y+192
30. Y=Y%192:SPOFS 1,0,Y,0
31. GOTO @LOOP
32. @FR
33. SPOFS 2,0,Y,0:SPOFS 2,A,Y,C/2
34. RETURN
35. @MM
36. SPCHR I,13
37. SPOFS I,99+RND(99),-20+256*RND(2),0
38. SPOFS I,99+RND(99),-20+256*RND(2),99+RND(C)
39. RETURN
40. @HIT
41. SPCHR I,248
42. SPANIM I,8,6,1
43. RETURN
44. @END
45. BGMPLAY 6
46. WAIT 360
47. FOR I=0 TO 16:I=BUTTON(0):NEXT
48. GOTO @INIT

So far, I'm using standard graphics. It's very convenient that the graphics are all built-in. However, there is always a way to have custom made graphic. I won't list the source code, but check out the QR made for this game.

http://petitcomputer.wikia.com/wiki/Santa_Helper