I finished the Crystal Cavern. Levels are rather short and there is no extra content in them but I focused on different things.
- Sound and music
- Full gamepad support (including the menu)
- Super fancy rotating camera in the pause menu (the only part done in C++)
- Localization to the Czech language
- Switch to full screen and windowed mode
- Portal which is used as the level ending point
- Persistent state of unlocked levels
