For a beginner, this game is decent! You can play the game from start to finish, with no major bugs and there's a clear objective.
If you wanted to take this game to the next level, I would have liked to see a more unified theme, better visuals and sfx. Maybe add something to engage the player a bit, because right now the player is most likely on autopilot, at least in the later levels where you can see the gem from where you spawn. You just have to walk from point A to point B and that's not engaging. The ending feels a bit forced to match the theme of the game jam and doesn't really tie into the gameplay.
Also first thing I tried to do was to press ESC to change mouse sensitivity : ) (which didn't work)
Overall, solid work though.