Well this program that Devilmarkus wrote was the kind of thing I was thinking of:

`10 RANDOMIZE 2011:MODE 0:FOR t=0 TO 15:INK t,0:NEXT:INK 1,26:INK 2,9:INK 3,18`

20 k=20:FOR x=0 TO 640 STEP 4:p=RND*2:PLOT x,0,2:DRAW x,20+k+p:PLOT x,20+p+k,1:DRAW x,22+p+k:IF x>300 AND x<600 THEN k=k+0.25 ELSE IF x<150 THEN k=k-0.5

30 pf=INT(RND*2011):IF pf>500 THEN GOTO 60 ELSE IF pe<4 THEN pe=4

40 g=INT(RND*8)+1:FOR y=400 TO 22+p+k STEP -g:PLOT x+RND*16,y,pe:y=y-RND*8:pe=pe+1:IF pe > 15 THEN pe=4

50 NEXT y

60 FOR l=0 TO RND*4:PLOT x,RND*(18+p+k),(RND*1)+2:NEXT:NEXT

70 a=4+s:FOR t=4 TO 15:IF t=a THEN INK t,26 ELSE INK t,0

80 NEXT:CALL &BD19:s=s+1:IF s>11 THEN s=0

90 GOTO 70