Week 6 Changes

- Health Bar & Game Over UI:

Health bar is now responsive when colliding with enemies. In other words, health bar drops 20% each time player touches enemies. Once health bar is empty, the game over UI will pop up and clicking restart will restart the game.

- Timer:

Implemented a timer functionality in the game. The player will have to survive until the timer runs out. Once the timer runs out and player is still alive, player wins and a UI will pop out to prompt player player again. 

- Info UIs & Pause game:

Implemented UIs that instruct player the basic controls for this game. To call out the instruction UI, press ESC. When the instruction UI is active, the game will pause.

- Bug fix:

Projectiles only get destroyed when they collide with obstacles in the scene. Fixed a bug that projectiles won't get destroyed when they are flying out of the map.