Spike Ambush Prevention Patch

Balancing changes:

- changed tile sprites so that spikes are easier to see

Bugfixes:

- fixed odd behavior where boss would immediately fire into a wall after spawning

Quality of Life:

- added restart hotkey (press enter to restart or play again)

In the meantime, I'll work on adjusting the turrets for the next balance patch, so hit me up if you have any balancing suggestions.