Dragon curve

graphsize 900,900

color yellow

rect 0,0,900,900

color black

fastgraphics

order=15

Dim s(2^order+1)

s[1]=1 : s[2]=1

for n=2 to order

a= 2^n-1 : b=2^(n-1)+1

for g= a to b step -1

s[g]= abs(s[2^n-g]-1)

next g

s[2^n]=1

next n

Zoom =3 : angle=180

x1=110*Zoom : y1=90*Zoom

for g= 1 to 2^(order)-1

refresh

gosub lines

if s[g]=1 then angle =angle+90

if s[g]=0 then angle =angle-90

next g

lines:

r = (angle/180)*pi

y2=y1 + (sin (r))*Zoom

x2=x1 - (cos (r))*Zoom

line x1,y1,x2,y2

x1=x2

y1=y2

return