Behind The Castle 🏰

https://www.dwitter.net/d/17329

JavaScript...

t*=540
a=t-14200
w=a0&a<1800
x.fillStyle=`hsl(${b?9:9-t/69} ${b?9:69}% ${b?w*9:90+C(t/T)*9-t/200}%`
x.fillRect(b?199+a:t%2e3,b?600-(a**.1*61%2+7|0)*49*(w?a/T:1):t/19+C(t/399)*39,-9,T=1e3)