EDIT: Make a game in 10 lines or less.

[LooseCaboose]

Space invaders clone in 15 lines (I might work on it some more and try and cut it down a few). There are only five enemies in a single line and they cant shoot back, so the game is quite easy. The game uses double buffered screen 7 graphics, has sound and gets harder as the game progresses. Once again, the game wont end if you win, but it will if you lose.

Controls:
Z - move left
X - move right
Enter - Shoot
Esc - Quit

Code:

1 FOR i = 0 TO 22
2 IF i = 0 THEN SCREEN 7 ELSE IF i = 1 THEN px = 160 ELSE IF i = 2 THEN sy = -5 ELSE IF i  = 3 THEN edir = 1 ELSE IF i = 4 THEN DIM ex(0 TO 5), ey(0 TO 5), ea(0 TO 5) ELSE IF i = 5 THEN d = 5
3 IF i = 5 THEN ey(0) = 10 ELSE IF i = 6 THEN ey(1) = 10 ELSE IF i = 7 THEN ey(2) = 10 ELSE IF i = 8 THEN ey(3) = 10 ELSE IF i = 9 THEN ey(4) = 10 ELSE IF i = 10 THEN ey(5) = 10 ELSE IF i = 11 THEN e(0) = 40 ELSE IF i = 12 THEN ex(1) = 80 ELSE IF i = 13 THEN ex(2) = 120 ELSE IF i = 14 THEN ex(3) = 160 ELSE IF i = 15 THEN ex(4) = 200 ELSE IF i = 16 THEN ex(5) = 240 ELSE IF i = 17 THEN ea(0) = 0 ELSE IF i = 18 THEN ea(1) = 1 ELSE IF i = 19 THEN ea(2) = 1 ELSE IF i = 20 THEN ea(3) = 1 ELSE IF i = 21 THEN ea(4) = 1 ELSE IF i = 2 THEN ea(5) = 1
4 NEXT
5 FOR k = 0 TO 14
6 IF k = 0 THEN SCREEN 7, , 1, 0 ELSE IF k = 1 THEN PCOPY 2, 1 ELSE IF k = 2 THEN IF sy = 175 THEN sx = px ELSE ambiguity = 1 ELSE IF k = 3 THEN IF sy <> -5 THEN sy = sy - 5 ELSE ambiguity = 1 ELSE IF k = 4 THEN DRAW "C10BM=" + VARPTR$(px) + ",180F10L20E10BD5P10,10"
7 IF k < 6 THEN GOSUB drawEnemy ELSE IF k = 7 AND INP(96) = 44 AND px > 20 THEN px = px - 5 ELSE IF k = 8 AND INP(96) = 45 AND px < 300 THEN px = px + 10 ELSE IF k = 9 AND INP(96) = 28 AND sy = -5 THEN sy = 175 ELSE IF k = 10 AND INP(96) = 1 THEN END
8 IF k = 6 AND POINT(sx, sy) = 13 THEN SOUND 100, 1 ELSE IF k = 7 AND POINT(sx, sy) = 13 THEN e = (sx - ex(0)) / 40 ELSE IF k = 8 AND POINT(sx, sy) = 13 THEN ea(e) = 0 ELSE IF k = 9 THEN PSET(sx, sy), 12 ELSE IF k = 10 THEN PCOPY 1, 0 ELSE IF k = 11 THEN SCREEN 7, , 0, 0 ELSE IF k = 12 THEN time = TIMER ELSE IF k = 13 AND TIMER < time THEN GOTO 8 ELSE IF k = 14 THEN GOTO 5
9 NEXT
10 changeDir: FOR i = 0 TO 9
11 IF i = 0 THEN IF edir = 1 THEN edir = 2 ELSE edir = 1 ELSE IF i = 1 THEN ey(0) = ey(0) + d ELSE IF i = 2 THEN ey(1) = ey(1) + d ELSE IF i = 3 THEN ey(2) = ey(2) + d ELSE IF i = 4 THEN ey(3) = ey(3) + d ELSE IF i = 5 THEN ey(4) = ey(4) + d ELSE IF i = 6 THEN ey(5) = e(5) + d ELSE IF i = 7 THEN IF ey(0) >= 170 THEN END ELSE ambiguity = 1 ELSE IF i = 8 THEN d = d + 2 ELSE IF i = 9 THEN RETURN
12 NEXT
13 drawEnemy: FOR j = 0 TO 7
14 IF j = 0 THEN kx = ex(k) ELSE IF j = 1 THEN ky = ey(k) ELSE IF j = 2 THEN IF ea(k) = 1 THEN DRAW "C13BM=" + VARPTR$(kx) + ",=" + VARPTR$(ky) + "F5G10E10H5G5F10H5BU5P13,13" ELSE ambiguity = 1 ELSE IF j = 3 THEN IF edir = 1 AND ex(0) < 100 THEN ex(k) = ex(k) + 1 ELSE ambiguity = 1 ELSE IF j = 4 THEN IF edir = 1 AND ex(0) >= 100 THEN GOSUB changeDir ELSE ambiguity = 1 ELSE IF j = 5 THEN IF edir = 2 AND ex(0) > -20 THEN ex(k) = ex(k) - 1 ELSE ambiguity = 1 ELSE IF j = 6 THEN IF edir = 2 AND ex(0) <= -20 THEN GOSUB changeDir ELSE ambiguity = 1 ELSE IF j = 7 THEN RETURN
15 NEXT