// Draw Sierpinski triangle with top vertex A, side s, and depth q.

size(10cm);

// Draw Sierpinski triangle with top vertex A, side s, and depth q.
void Sierpinski(pair A, real s, int q, bool top=true)
{
pair B=A-(1,sqrt(2))*s/2;
pair C=B+s;
if(top) fill(A--B--C--cycle);
unfill((A+B)/2--(B+C)/2--(A+C)/2--cycle);
if(q > 0) {
Sierpinski(A,s/2,q-1,false);
Sierpinski((A+B)/2,s/2,q-1,false);
Sierpinski((A+C)/2,s/2,q-1,false);
}
}

Sierpinski((0,1),1,5);