There is a lot of brilliance in the basic action of this game. Everyone agrees the animations, the controls, the enemy feedback are great, but the game feels so good thanks to that, and a series of systems added into the game that are more subtle, like:
-the rally effect: you can recover some health you just lost by dealing damage to the enemies quickly. This allows for a somewhat fast, agressive and fun style within a game that otherwise is hard enough to be better to play conservatively.
-death prevention: if someone would kill you in one hit when you are over 25% hp, you are left with 1 hp and with a time slow down, enough to save the situation.
-interrupt system/breach: you can briefly stun enemies by dealing a big amount of damage to them while they are doing an attack or defense animation. Some weapons are better/worse in doing this, and some enemies are better/worse at resisting it.
-speed bonus: kill several enemies in a limited amount of time, and you win a speed bonus, which allows you to maintain the bonus even more time.
It's thanks to all this that the flow of the game is so good.
It also has a nice environment interaction layer that increase the variety of the action, like:
-breaching a door and stunning who is behind it.
-break a ceiling and do a lot of damage to whatever is below it.
-dive from the heights to do damage on the ground in aoe.
-Pull or push enemies with some items and weapons to make them fall from ledges and receive damage.
-Water interact with fire, cold and electricity damage in the way you would expect. Fire also interact with oil.
The variety is also superb for an action roguelite, a few examples of different builds you can do:
-You can try to max hp by balancing correctly your stats and take then the +50% hp mutation.
-You can try go full offensive by investing in only one stat (red/purple/green), killing everything in one or two hits but being a glass cannon.
-You can use a combination of stuns like frost blow and heavy melee weapons.
-Or quick weapons like the dagger or the gauntlets and try to interrupt their attacks, rolling to avoid any enemies.
-or you can use shields to block damage, parrying hits and even returning projectiles.
-You can use ranged weapons, like bows that have to be fired on the precise moment, or that do extra damage at long or close range.
-Or find a great combo with the random affixes for the weapons and items, that for example apply bleed, poison and fire all at the same time.
-Maybe you prefer to use two turrets and let them kill everything for you while you try to stat at the optimal range.
-Some items are interesting for the defensive ways they ca be used, like the explosive decoy that makes you invisible or the Wings of the crow that allow for limited floating around.
Finally, it has the best group of
enemies in a game from the last years. Each one has a clear gameplay niche that isn't covered by any other one. They all have different attack patterns, and special abilities.
There are enemies that:
-attack you in melee, leaps (zombie)
-attack you with ranged weapons (archer)
-throw cluster or normal explosives (bombardier, grenadier)
-have ranged attack that goes through walls. (inquisitor)
-have a chained attack combo (slasher)
-make a dash charge against you (bat)
-fly around (bat, corpse fly, etC)
-explodes in close proximity to you (kamikaze)
-teleports close to you (Runner)
-teelports you close to him (golem)
-have a wide aoe attack (tornado knight, mushroom)
-spawns more enemies by itself (Hammer)
-can bury on ground (Scorpion)
-spawn explosives on death, or spawn more enemies on death (purulent zombie, worm)
-have a side that deals damage to you if you melee them (Thorny) or have an invulnerable side (shield zombie)
-make other enemies invulnerable (dummy enemy)
-Makes enemies invisible (fog guy)
Hell, I think lots of other roguelikes or even normal action or action rpg games could learn a bit from Dead Cells in how important is to have truly different enemies to mix up the action.