It randomly generates a maze ! Worth mentionning that the script is small enough to be in tweet !!
c.width=c.height=600;u=20;w=60;for(i=0;i<w;i++)for(j=0;j<w;){o=Math.random()*2>>0;a.moveTo(j*u,(i+o)*u);a.lineTo(++j*u,(i+1-o)*u)}a.stroke()
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