Hi, thanks for playing and your comment. This game was developed in three weeks of spare time. So we didn't add some Optional features like change key binding, also maybe still have some small bugs. We will improve them in the future!
If you die in the middle of a level, it will only fill your hp to the value when you first time reach the level. And the hp will keep it to next level. The only way to add hp is get a health pickups. If you think its too hard, we will consider to adjust the difficulty.
cheers, have fun!