I think there's a bug with the id() condition, where the condition stops working after the player has died once. In my latest level, each boulder pushed into the starting pit should activate a checkpoint, and this works fine until the player dies once. After that, none of the checkpoints seem to work (you can't activate any new checkpoints)

These docs have been moved to http://www.droidfreak36.com/HATPC/events.php and updated with the events added since they were created.