Guide by BetaM.
- Gems are not required to see the game's true ending.
- Gems only need to be collected once, they don't respawn or disappear from the menu upon death.
- You can backtrack to most levels, however after you reach the 4th hub, you can't go back to the previous ones until the game is beaten.
- All gems can be acquired after beating the game, and all collected gems stay that way after the credits.