setup=_=>createCanvas(w=200,w)+pixelDensity(1)+background(9,a=15e4)+rect(0,50,50,d=99)
draw=_=>{s='copyWithin'
loadPixels()
p=pixels
for(x=3;x<15e4;x+=9+p[a])p[s](x-w-p[a]*2,x+p[a],x+w)[x]=x%w<d?0:w;
p[s](a,1,2e3)[a-1]>d&&p[['reverse',s][p[8e4]%2]]()
updatePixels()}//#つぶやきprocessing