Pretty neat game, but why does the player have to save the checkpoints by explicitly pressing a button? Why not activate them automatically when touched?
I considered doing it that way, but I think it's a little more satisfying to have to explicitly press a button - like yelling "SAFE!" when you touch base in tag.
It also means activating the save points takes a little extra thought/time, so if you're going for a speedy playthrough you have an incentive to skip some or all of the save points. I think that trade-off is interesting!