LOOP.BAS

10 REM LOOP
20 GR:HOME:COLOR=6
30 STARTX=0:STARTY=0:EX=39:EY=39:SIDE=1
40 PX=STARTX:PY=STARTY
50 PLOT PX, PY
60 IF SIDE=1 THEN GOSUB 200
70 IF SIDE=2 THEN GOSUB 300
80 IF SIDE=3 THEN GOSUB 400
90 IF SIDE=4 THEN GOSUB 500
100 IF STARTY = EY THEN END
110 GOTO 50
200 REM TOP -----
210 IF PX = EX THEN SIDE = 2
220 IF PX = EX THEN EX = EX - 1
230 IF PX < EX THEN PX=PX+1
240 RETURN
300 REM RIGHT ---
310 IF PY = EY THEN SIDE = 3
320 IF PY = EY THEN EY = EY - 1
330 IF PY < EY THEN PY = PY + 1
340 RETURN
400 REM BOTTOM --
410 IF PX = STARTX THEN SIDE = 4
420 IF PX = STARTX THEN STARTX = STARTX + 1
430 IF PX > STARTX THEN PX = PX - 1
440 RETURN
500 REM LEFT ----
510 IF PY = STARTY THEN SIDE = 1
520 IF PY = STARTY THEN STARTY = STARTY + 1
530 IF PY > STARTY THEN PY = PY - 1
540 RETURN