perl -e 'for (1..300) { $x = $_/300; $y = 1-$_/300; print "$n\n"; $n = sprintf("%03d", $_); `ppmmake 0,$x,$y 50 50 | ppmtogif >$n.gif`}'
gifsicle --loop=forever --colors 256 --background 000 -d 2 <001-300>.gif `ls *.gif | tac`  >anim.gif