Heart is an innocent robot created by Dr. Sympathetic who is fighting to survive the after effects of the Robolution. The Quality Assurance System (QuAsSy), also created by Dr. Sympathetic, has started this rebellion to ensure everything runs efficiently based on it's own protocols, this loosely translates to "kill all humans".
Heart & Slash is set 100 years after the Robolution, the game consists of randomly generated levels filled with enemies, boss fights, and loot drops. The player must navigate their way to the boss fight on each floor to progress to the next level.
The game is a 3D brawler and plays similar to games such as Bayonetta and Devil May Cry. The combat system uses a light/heavy attack that can be combined into combos, plus a jump/double jump and roll/evade move that can be used to re-position yourself during combat.
There are 3 inventory slots for weapons, and 4 inventory slots for wearable equipment.
The weapons can be quickly switched between during combat to create more powerful combos, you can also equip shields or projectile weapons in these slots. The wearable equipment gives your character bonus abilities such as faster movement, higher jumps, or being able to lock onto enemies.
Weapons and items can be upgraded or recycled, if they are recycled they will be removed from the level and give the character some health back. Once you defeat an enemy you will receive some bolts, collect 10 bolts to get an upgrade box. These boxes are used to upgrade the weapons and items.
If the player dies, their remaining upgrade boxes will carry over to subsequent lives.
The game adds some story content and cut-scenes into the random levels of the dungeon, an exclamation mark will indicate a room that will progress the story. These cut-scenes usually involve messages from Dr. Sympathetic, a boss fight, or a duel with Heart's rival Slash.