Two things I need to start with:
1. It's short. Like really short.
2. You are probably going to want a controller.
Nonetheless, it's fairly fun, and at $8 may be worth a look if you want a quick arena brawler with a bit of customization when it comes to attack set.
I probably need to explain that. The game works on a magic sword (well, they're not all swords, but that's what I'm going to call them) system, not unlike Ys 6, and each sword has a single ability tied to it. By holding down your button for special attacks and pressing one of the four main buttons (jump, bomb, attack, and dash), you'll use one of the abilities of the swords you have equiped. When using an ability, you switch to the sword that ability is tied to, but aside from abilities, the swords aren't actually noticeably different (if at all).
There's really only probably about 8 enemies in the game in total, including bosses. There's 3 bosses, a melee mob, a ranged mob, 2 big bads, and a flier. There are some color variants that correspond to how tough the enemy is, but that's it really.
The game has a few mods to play with. There's story, arcade, challenge, score attack, survival, and bonus. Story mode is simply climbing the tower, you must complete this mode under 10 minutes to actually reach the ending. Arcade mode is story with the story sections removed. Challenge is simply a set of challenges for the player to complete. Score attack is attempting to get a high score in 3 minutes. Survival is what you would expect. Bonus mode also serves as an extension to story mode in which you have an AI controlled partner. Not all modes are available until certain condtions are met. Bonus doesn't unlock until beating Story mode with both characters under 10 minutes.
It should be possible to play scrore attack and survival in co-op, but I've not personally tested it.
On the topic of characters, aside from aethetics, they're mostly the same. Their swords, although different in look ,end up doing the same things for the most part. There's a few differences in the speed, range, and power of the attacks, but in the end I found myself doing a knock up, followed by an aerial AoE, followed by a ground slam on both characters, with another weapon for ground based AoE. There's a small variations to some other their weapons (one character has an aerial dash and the other has a ground dash), so while the characters aren't significantly different, if you're building a specific attack set to chain together, picking one over the other may matter.
In any case, it's a simple game without a whole lot of content, but it does what it does pretty well, so at the price that it's at, it may be worth a look.