A bunch of QOL features/polish

To be completely honest, the first version of my game was probably made in 7-10 hours, max. I'm a perfectionist, so I tried to make it feel polished, but ultimately, the controls were clunky and it could've been a much better game in general. So, I decided to fix many of the major issues and add some new content too!

Additions

+ A new wave system (see Tweaks)
+ "Heavy" variants of enemies that spawn from Wave 5 onward
+ Frozen ponds (and ice physics)
+ A crosshair (see Tweaks)

Tweaks

+ Increased the amount of snowballs you can have at one time (although you still start with 5)
+ Enemies can now spawn on any tile (see Fixes)
+ The player now pivots to face the cursor/crosshair when throwing snowballs
+ Enemies now spawn in less-frequent waves. When one is completely cleared, the next spawns, otherwise it spawns after 30s

Fixes

+ Fixed an issue where enemies would spawn inside of each other due to limited numbers of spawn points

Known Issues

+ The game can be laggy when dealing with or spawning large numbers of enemies