A folding tree with three sets of recursive branches.
When rotated enough they form a Sierpiński triangle!
Cartridge code (209 chars):
function r(x,y,d,a,b,c)local e,f=x+cos(a)*d,y+sin(a)*d line(x,y,e,f,15-c) for j=-b,b,b do if(c>6)break r(e,f,d/2,a+j,b,c+1)end end camera(-64,0)::★::cls() s=64 r(0,64+s,s,.25,.225-sin(t()/5)/9,0) flip() goto ★