window origin "lb"
open window 640,512
setup():mystify()

sub setup()
'====setup arrays for polygons====
dim x(24)
dim y(24)
dim dirx(24)
dim diry(24)
'====set initial directions for corners====
for a=1 to 4
read dirx(a)
read diry(a)
next a
for a=5 to 12
dirx(a) = dirx(a-4)
diry(a) = diry(a-4)
next a

for a=13 to 16
read dirx(a)
read diry(a)
next a
for a=17 to 24
dirx(a) = dirx(a-4)
diry(a) = diry(a-4)
next a

'====set initail positions for corners====
for a=1 to 24
read x(a)
read y(a)
next a

'====setup scroll text===
txt$=     "Thanks to Adam Lay for provideing the "
txt$=txt$+"excelent yabasic.co.uk and Nick Simpson for " 
txt$=txt$+"provideing the colourful backdrop. Cheers guys"

textend=-30-(len(txt$)*10)
tx=640
ty=25
end sub

sub mystify()
repeat
clear window
draw()
'====move the corners====
for a=1 to 24
x(a)=x(a)-dirx(a)
y(a)=y(a)-diry(a)

'====check for colisions====
if x(a)<100 dirx(a)=0-(dirx(a))
if x(a)>540 dirx(a)=0-(dirx(a))
if y(a)<100 diry(a)=0-(dirx(a))
if y(a)>412 diry(a)=0-(dirx(a))
next a
scrolltxt()
db()
until (peek("port1")=16384)
end sub

sub draw()
cc=cc+0.1
red=50+50*sin(cc/2)
blu=50+50*sin(cc/3)
grn=50+50*sin(cc/4)
setrgb 1,red,30,30
setrgb 2,30,grn,30
setrgb 3,30,30,blu
gtriangle 0,0 to 640,512 to 0,512
gtriangle 0,0 to 640,512 to 640,0

clear fill rectangle 75,75 to 562,437
setrgb 1,23,23,23
fill rectangle 100,100 to 540,412

c=c+0.15
setrgb 1,75+50*sin(c/15),75+50*sin(c/17),75+50*sin(c/20)

for a=0 to 20 step 4
for b=1 to 3
if a>=12 setrgb 1,75+50*sin((c+75)/10),75+50*sin((c+75)/15),75+50*sin((c+75)/20)
line x(b+a),y(b+a) to x((b+1)+a),y((b+1)+a)
next b
line x(a+1),y(a+1) to x(a+4),y(a+4)
next a
end sub

sub scrolltxt()
setrgb 1,75+50*sin(c2/10),75+50*sin(c2/10),75+50*sin(c2/10)
c2=c2+0.75
text 100,83,"PRESS 'X' TO QUIT"
setrgb 1,250,250,250
text tx,ty,txt$
tx=tx-2
if tx<txtend tx=640
end sub

sub db()
setdispbuf draw
draw=1-draw
setdrawbuf 1-draw
end sub

'====data for the directions====
data -1,-1,1,1,1,-1,-1,1
data 1,1,-1,-1,-1,1,1,-1
'====data for the positions====
data 200,200,200,300,300,300,300,200
data 205,205,205,305,305,305,305,205
data 210,210,210,310,310,310,310,210
data 150,150,250,150,150,250,250,250
data 155,155,255,155,155,255,255,255
data 160,160,260,160,160,260,260,260