10  CLS 
20  SCREEN 12
30  X1 = 1 
40  X2 = 51 
50  Y1 = 1 
60  Y2 = 11 
70  LINE (X1,Y1)-(X2,Y2),15,BF 
80  DO WHILE INKEY$ <> "q" 
90  MOTION$ = INKEY$                    REM I'm thinking Of adding a small while loop around this line
100 IF MOTION$ = "4" THEN GOSUB 140 
110 IF MOTION$ = "6" THEN GOSUB 190 
120 LOOP 
130 END 
140 LINE (X2,Y1)-(X2,Y2),0,BF 
150 X1 = X1 - 1 
160 X2 = X2 - 1 
170 LINE (X1,Y1)-(X1,Y2),15,BF 
180 RETURN 
190 LINE (X1,Y1)-(X1,Y2),0,BF 
200 X1 = X1 + 1 
210 X2 = X2 + 1 
220 LINE (X2,Y1)-(X2,Y2),15,BF 
230 RETURN