Big Update

Fixes:

-Can no longer place towers in restricted places.

Added: 

-Five waves, 2 new normal enemies and a boss enemy.

-Missile Tower.

-Hills to place Missile Tower on.

-Player can now leave the game by pressing "ESC".

-Health, money and other variables.

-UI for new variables.

-Shop UI for Towers.

-Added blue plane around the level to act as a place-holder water effect.

Changed:

-Towers now target farthest along enemy.

-Slightly changed enemy path.

-Tower colour scheme is different.

-Slightly reduced lighting.