Fixed some bugs and added polish. Changes:

- Allow player to use W to shoot up after unlocking in level 1.

- Added an arrow that is instantiated when all enemies killed, pointing to the end platform.

- Added damage UI popups when player and enemies are hit.

- Added screenshake for when player is hit and when bullet is fired.

- Added health text to the health bar.

- Added red vignette effect through post-processing when on low health.

- Added heart beat sfx when low health.

- Added sprite animation when player uses ability.

- Added sfx when time is stopped and started with the ability.

- Added sfx when time left is less than 5 seconds.

- Added animated text that shows when R is held to restart.

- Added text that is tweened on screen if player tries to shoot when they have 0 bullets left.

- Created tutorial level which introduces the player to the controls and mechanics.