Update Contents:
Modified grass and dirt sprite details
Fixed details of some building sprites
Corrected some sprite replacement issues
Adjusted survival mode rules (enemy levels now gradually increase over time)
[Barracks, Mill, Lumber Mill, Stone Quarry] no longer require research in the [Research Window]; these buildings are now available from the start
[Wooden Wall] maximum HP changed from 200 to 100
[Defense Tower] research requirement updated (stone requirement changed from 200 to 500; level 2 no longer requires player level)
Modified parts of the game UI