BASIC8 Chastity Polygon

I translated my spinning polygon routine by looking at the C version and copying everything over to BASIC syntax. It also draws a checkerboard behind the polygon because I left the code from my previous project there.

REM BASIC8 port of Chastity's Regular Polygon

'the width and height of the program
'this is set in stone by the BASIC8 creator so these never change
width=160,height=128

'declare my 2 color palette for the checkerboard
palette=list()
push(palette,rgba(0,0,0))
push(palette,rgba(255,255,255))

rem new section for declaring the polygon variables
cx=width/2 'center x of the polygon
cy=height/2 'center y of the polygon
radians=0 'the current rotation angle of the polygon
radius=height/2
polygon_points = 8
polygon_step = 3 'for how the points are stepped through,applies to star polygons
polygon_color=rgba(255,0,0)
'arrays of x and y points
dim xpoints(polygon_points)
dim ypoints(polygon_points)

'old section that does the checkerboard from my other project
rectsize=8
def update()
index=0
y=0
while y<height
index1=index
x=0
while x<width
rectfill x,y,x+rectsize,y+rectsize,palette(index))
index=BXOR(index,1)
x=x+rectsize
wend
index=BXOR(index1,1)
y=y+rectsize
wend
rem end of checkerboard section

'fill the point arrays with correct values using trigonometry
i=0
while i<polygon_points
f=i/polygon_points
angle=2*pi*f
angle=angle+radians
x=sin(angle);
y=cos(angle);
x=cx+x*radius;
y=cy-y*radius;
'print i;
'print "angle=",angle;
'print "x=",x," y=",y;
xpoints(i)=x;
ypoints(i)=y;
i=i+1;
wend
rem now all points are set up.

rem next draw triangles
i=0
while i<polygon_points
i1=(i+polygon_step) mod polygon_points;
trifill cx,cy,xpoints(i),ypoints(i),xpoints(i1),ypoints(i1),polygon_color
i=i+1;
wend

'change the rotation
radians=radians+0.03

enddef
update_with(driver())

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