CHANGES
added a popup-window when beating easy mode, with an option to leave and swap to hard mode or stay in the last (infinite) wave
changed the difficulty for energy trade upgrades -> difficulty/energy before: 3/5, 5/10, 7/15, 10/20 and 15/25 now -> 5/10, 8/20, 10/30, 12/40 and 14/50 (this makes higher tiers actually more efficient, before it was literally bs)
added a new visual indicator for the red end-boss of easy mode
BUG FIXES
fixed a layering issue where rockets would clip through ui
fixed an upgrade's icon being missing