Rather than increase skill points per level (which would make the game even EASIER T_T), how about simply unlock a mode where spawns have double hp or some other bonus?
Better yet, unlock a bonus level when you get all brilliants that is incredibly difficult. This game is just too easy with the hotkeys now.
No upgrades and tedious play... Not to mention the scores don't reward shrewd and quick play. If you want five stars on a level you have to get both kills and speed... Why isn't speed good enough? 2/5
 "Command & Control"){kind=icon}
 "Villainous"){kind=icon}
 "Cursed Treasure: Level Pack!"){kind=icon}
 "Bug War 2"){kind=icon}