Strange Attractor

A one-evening pico-8 toy for #tweettweetjam, in 555 characters of source code.

• Use the arrow keys to move an attractor.
• 🅾️ (Z on most keyboards) to select a different attractor.
• ❎ (X on most keyboards) to adjust size.

Source code:

c=circfill h=1x=0w=1e={25,89,55}f={80,68,20}g={8,3,6}p={}for i=1,5do p[i]={}end function _update() b=btn()e[h]+=b%4\2-b%2f[h]+=b%16\8-b%8\4g[h]+=w*(b%64\32)if(btnp(4))h+=1 if(h>#e)h=1 if(abs(g[h])>15)w=-w g[h]+=w for n=1,80 do if(x<1or#p[5]>300)x=1y=59+rnd(8)u=2v=0deli(p,1)p[5]={} x+=u y+=v add(p[5],{x,y})for i=1,#e do k,l=e[i]-x,f[i]-y m=g[i]/sqrt(k^2+l^2)/4a=atan2(l,k)u+=m*sin(a)v+=m*cos(a)end end end function _draw()cls(1)for i=1,#p do if(i<=#e)c(e[i],f[i],abs(g[i]),sgn(g[i])+1) for j=1,#p[i] do q=p[i][j]pset(q[1],q[2],i%8+7)end end c(e[h],f[h],1) end