The premise alone was very enticing, but unfortunately with a cost of 5 dollars you kinda get what you pay for. This game is tedious, it's repetitive, and it's boring. In my 2 hours of play time I finished everything and I enjoyed very little of the experience.
Gameplay boils down to getting to play a Boss, being forced to unlock the most mundane features like healing, or any kind of notable abilities a Boss battle might have other than a basic attack. You only get the ability to buy new features if you kill enemies, so you pretty much have to start on Easy and climb your way up, then after you unlock everything you have what can kinda resemble some Boss mechanics from games in a bygone era. Then you move on to the next boss, get to keep none of the points you earned in the previous bosses to buy abilities quicker, then grind your way to making the new boss feel like an actual Boss battle before moving on to the next one and repeating it over and over 6 times. The abilities are simple, they are boring, and they should be there to begin with and build up to cooler things like stage hazards or something.
You basically change backgrounds slightly, the music stays the same as there is only 1 or 2 songs in the entire game, and there are no actual Boss-like mechanics to be found. You don't get any AoE abilities even, except for the Robot with his stun and push back. There is nothing flashy, no different phases of your boss fight or multiple health bars, it's just wave after wave of uninteresting enemies that come in a random pair of 2. The only time I was ever truly engaged in the fights was that for some reason the Monk in the first 2 bosses is Fire Proof and the Rogue goes invisible sometimes. The Monk being fire proof matters for exactly 1 boss, but hey at least it's something to kinda play around? There is no engagement, it's just a tedious slog to the finish.
If this game was 1 dollar, I'd recommend it for someone that wants to bash their head against the wall with minimal physical trauma. As it is, it's like a mobile game on PC. I truly wish the concept was more flushed out, like maybe you have some involvement when the heroes walk through the level in the top right corner, like a bowser fireball rushing through the level, or dealing damage to them by upgrading your defenses so your dungeon hurts them before they get to you. Maybe have the ability to jump out the arena, your mobs deal with them a bit as you hurl effects at them off from the sidelines, jump back in and the heroes use abilities too. Maybe the paladin shields it's allies, the power sword space marine guy can grab your minions and throw them around, maybe the jedi staff guy can push you away or pull you towards it. I don't know, just something, anything to make the fights more engaging rather than me just mashing the same buttons over and over and over again until I win or lose.
P.S. please give each boss a unique boss song, listening to the same ringtone jingle for more than 15 minutes is kinda annoying. Yes, I can turn it off, but any game that has music so bothersome that you legit are better off not hearing it needs to improve.
