OPTION BASE 0
RANDOMIZE TIMER
SCREEN 13
pi = 3.1415926536#
piq = pi / 2
xmin = 4
ymin = 4
xmax = 316
ymax = 196
bc = INT(RND(1) * 15) + 1: c = 0
forcol:
fc = INT(RND(1) * 15) + 1: IF fc = bc THEN GOTO forcol
GOSUB background

x = xmax: y = ymax
n = 10000
DIM x(n), y(n), xf(4), yf(4)
FOR k = 0 TO 3

NEXT k

GOSUB box
n = 0

main:
        GOSUB getnumdir
        IF numdir = 0 THEN GOSUB trace
        IF numdir = 0 THEN GOTO xit

        d = INT(RND(1) * numdir) + 1
        ON dir(d) GOSUB dir1, dir2, dir3, dir4



        x(n) = x
        y(n) = y
        n = n + 1
        x = x + xf
        y = y + yf
        GOSUB box




GOTO main



xit:

'PAINT (xmin + 1, ymin + 1), fc, bc

delay = 0

keyin:
delay = delay + 1
k$ = INKEY$
IF k$ = "" THEN GOTO keyin
IF k$ = CHR$(27) THEN GOTO xit1
IF k$ = CHR$(32) OR delay = 2000 THEN RUN

GOTO keyin
xit1:

        END
trace:
        n = n - 1
        IF n = 0 THEN RETURN
        x = x(n)
        y = y(n)
        GOSUB getnumdir
        IF numdir = 0 THEN GOTO trace
RETURN

getnumdir:
        numdir = 0
        IF POINT(x + 4, y) >= bc THEN
                numdir = numdir + 1
                dir(numdir) = 1
        END IF
        IF POINT(x, y - 4) >= bc THEN
                numdir = numdir + 1
                dir(numdir) = 2
        END IF
        IF POINT(x - 4, y) >= bc THEN
                numdir = numdir + 1
                dir(numdir) = 3
        END IF
        IF POINT(x, y + 4) >= bc THEN
                numdir = numdir + 1
                dir(numdir) = 4
        END IF
RETURN


box:
        LINE (x - 1, y - 1)-(x + 1, y + 1), c, BF
RETURN

box1:
        LINE (xx - 1, yy - 1)-(xx + 2, yy + 2), c, BF
RETURN

dir1:
        LINE (x + 2, y - 1)-(x + 2, y + 1), c
        xf = 4: yf = 0
RETURN

dir2:
        LINE (x - 1, y - 2)-(x + 1, y - 2), c
        xf = 0: yf = -4
RETURN

dir3:
        LINE (x - 2, y + 1)-(x - 2, y - 1), c
        xf = -4: yf = 0
RETURN

dir4:
        LINE (x - 1, y + 2)-(x + 1, y + 2), c
        xf = 0: yf = 4
RETURN

background:
        LINE (xmin - 2, ymin - 2)-(xmax + 2, ymax + 2), bc, BF
        RETURN

        FOR y = ymin TO ymax / 2 STEP 4
                FOR x = xmin TO xmax STEP 4
notgrey:
                        c = INT(RND(1) * (16 - bc)) + bc
                        IF c = 8 THEN GOTO notgrey
                        xx = x
                        yy = y
                        GOSUB box1
                        xx = xmax - x + 2
                        yy = ymax - y + 2

                        GOSUB box1
                NEXT x
        NEXT y
c = 0
RETURN