Interesting game concept. Some things I'd suggest
- Create a Pause Menu that allows the player to go back to the main menu. Not sure why but sometimes when I tried to click on the button for level 2, it pressed tutorial.
- UI Buttons should change color more noticeably when highlighted.
- Add some obstacles in your levels and allow your character to move upward and downward instead of just simply going straight. You can use the arrow keys for this.
- Link your breath action to a keyboard button like spacebar
- Something fun I thought of was to have some sort of music that plays based on the players distance from the shark (if you're further than certain distance then the volume is just 0%, but if he's right on your tail play volume at 100%)
Possible Bugs:
- When the player slows down from lack of oxygen he eventually starts going backwards.