10 GRAPHICS 9
11 Y=0:ADD=1:C=0
30 COLOR C
40 PLOT 0,Y
50 DRAWTO 79,Y
51 C=C+ADD:Y=Y+1
52 IF C=16 THEN ADD=-1:C=14
53 IF C=-1 THEN ADD=1:C=0
60 IF Y<191 THEN GOTO 30
70 REM --------------------
80 X=25:ADD=1:C=0
90 COLOR C
100 PLOT X,0
110 DRAWTO X,191
120 C=C+ADD:X=X+1
130 IF C=16 THEN ADD=-1:C=14
140 IF X<56 THEN GOTO 90
150 REM --------------------
160 Y=192/2-15-1:ADD=1:C=0
170 COLOR C
180 PLOT 0,Y
190 DRAWTO 79,Y
200 C=C+ADD:Y=Y+1
210 IF C=16 THEN ADD=-1:C=15
220 IF Y<192/2+15+1 THEN GOTO 170
999 GOTO 999