Completely reworked enemy spawn system: no limits and (almost) no enemy trains — the longer you last in a stage, the harder and more fun it gets :)
Enemies expelled by the monument wave now grant experience, buffs, and boosters
New booster drop system, allowing much finer control over drop chances and making it easier to respond to feedback about parameters
Stat upgrades in the upgrade window are now significantly more effective
Skills obtained and equipped in previous runs are now saved
Active skill levels and leveling up, plus camera effects when skills are used
Gamepad support has been restored
Demo Update 3.5
Source: Steam Community (opens in a new tab)