After a quite a lot of hassle, I succeeded in making my timelapse (and the bash script to go with \o/). Stream it here at 25fps (here for avi download), and here at 8fps (here for avi download). The script I created to make the videos from the images is here (hope this helps). Next step if I have the motivation : make an update to the game (mainly to fix the difficulty problem), and write a postmortem ^^