Ancient Monolith

Inktober day 23 prompt: Ancient

Demo: https://dwitter.net/d/16281

for(z=frame!=1380,i=2e3;i--;x.fillRect(z?i:300+i/4,z?t?300+t*(t+q*4):0:I?99-i/9:15+i/30,1,2e3))I=i<600,q=S(a=i/19/t+S(t)*t/29),x.fillStyle=`hsl(${t?30:200} ${z*59}%${z?99-C(t?a:6)*20-t*3:I*39}%`