' Old paper surface
' made by Svjatoslav Agejenko
' in 2003.12
' H-Page: svjatoslav.eu
' E-Mail: svjatoslav@svjatoslav.eu
 
DECLARE SUB paper (x1%, y1%, x2%, y2%)
DEFINT A-Z
SCREEN 12
RANDOMIZE TIMER
FOR a = 0 TO 15
OUT &H3C8, a
OUT &H3C9, a * 3
OUT &H3C9, a * 3
OUT &H3C9, a * 2
NEXT a

1
x1 = RND * 600 + 20
x2 = RND * 600 + 20
y1 = RND * 400 + 40
y2 = RND * 400 + 40
IF x1 > x2 THEN SWAP x1, x2
IF y1 > y2 THEN SWAP y1, y2
paper x1, y1, x2, y2
GOTO 1

a$ = INPUT$(1)

SYSTEM

SUB paper (x1, y1, x2, y2)
yl = y2 + 1
z = 0
LINE (x1, y1)-(x2, y1), 0
LINE (x2, y1)-(x2, y2), 0
FOR y = y1 + 1 TO y2
c = 0
FOR x = x1 TO x2
p = p + 1
IF p > 23 THEN z = RND * 1: p = 0
c1 = POINT(x, y - 1)
c = (c1 + c) / 2 + (RND * (2 + (5 / y)) - (3 / (yl - y))) - z
IF c < 0 THEN c = 0
IF c > 15 THEN c = 15
PSET (x - 1, y), c
NEXT x
NEXT y

END SUB