Changes for version 0.3:

• Introduced build-able level 5 towers.
• Upgrade cost increases per tower level.
• Static shadows for turrets and trees.
• Tower effect when upgrade is available is a bit more obvious.
• Highlight when mousing over a tower.
• Tower health increases with each level-up - health is also replenished.
• All towers get bonus XP at end of level.
• Cogs are now rarer but more valuable.
• Option to skip level count-down with a bonus depending on how much time is remaining.