the "flow state" of the game is not hard to achieve and it feels great when it's active. there is a lot of variety to the builds you can create and it seems like most weapons and powers are effective in their own right or in combination with other weapons, powers, and mutations. the controls are top notch (even though the double jump is trash and misleading) which facilitates getting into that flow state. the level design is fantastic. each area ("biome") feels discrete from the others, most of them having unique mechanics and layouts, i.e. the clock tower being a mostly vertical affair, as opposed to more horizontal levels like the ramparts and promenade of the condemned. the progression system is well done, letting the player organically unlock new weapons, powers, and biomes by simply getting better at the game. great stuff. people should play this game