Implement level mode animations and styles

[reteps]

Completion Criteria

Create an exploding pwny animation on the correct flag submission that gets sucked up by the level bar.

Make the level bar sticky to the top / still visible even upon scroll - but condensed.

Upon leveling up, have a level bar do animation indicating level up. Potentially confetti and a "pop out" effect / graphic in the center of the screen saying "level up"

Relies on #9