I really like this game and especially the art is beautiful!
A few suggestions, I hope they're helpful:
* I, too, would have liked more checkpoints (I didn't realize there was one until I saw the comments). * Maybe also some kind of indication of how far the next checkpoint is, or how far the end of the level is? * At least once, I accidentally missed some of the dialogue. Maybe there could be some way to see previous lines, like maybe a window with a log of what the robot said? * As for changing the collision difficulty - even without using tiles, maybe you could use a different bitmap to encode the collision info? * Also, it's not obvious that making a large jump won't punish you for the hard fall. * Maybe if you press A/D for too long, then the meter could go back down, so if you miss the jump strength you wanted, you could get another chance?