Version 0.6 released

New features:

• Added difficulty option in game lobby.
• New turret upgrade window.
• Turret upgrade options for slowing tower and bomb tower.

Fixes:

• Turrets occasionally lost their targets.
• Spitter enemies would get confused and lose their targets also.
• Shooting mechanism now allows continual fire on a single mouse click.
• Connection errors now result in an error being displayed instead of silently dying.

Balancing:

• Everything. All enemies and turrets have had their damage, HP, cost, and upgrade XP values modified.