It's a chinese/taiwanese(one of those two) 2d mecha game. It's a very simple, fairly short(I'd say around 2-3 hours, it's 8 chapters of two 10 minute missions each. You have four attacks, two of which are melee(effectively non-customizable), a main gun(you also get secondary main guns that don't reload) and a secondary shoulder mounted weapon. You also get a boost gauge similar to a game like say Rocktron where holding R1 boosts you in whichever direction you're holding the left analog in. You can also block but I've rarely used it.
The game's really simple but doesn't play much to its mecha strengths. There's very limited customization. In terms of weapons you have three configurations of your main gun, a shitty mode, a high power low magazine mode and a medium power high magazine mode. For the secondary you have a shitty peashooter and a slightly less shitty pea shooter and a rocket launcher. For your melee weapons you don't really have a choice, you start off with a shield bash and a dumb punch and then they get upgraded a few levels into the sword and electric shield bash and there's absolutely zero reason not to pick those. The parts where you have the most amount of customization are your mods and consumables. Consumables are meh, you can't go wrong with the health pack and the rest are pretty situational. Mods are just stat boosts and unless you pick boost enhancements and gun/melee enhancements you're likely doing it wrong.
You also get to pick one mech and one mech only, which is strange because you can tell there are a lot of mech classes with their own abilities and movesets. Turns out you can use those, in multiplayer. In singleplayer you're stuck with the generic gundam instead of the infinitely more interesting red melee-only mech that your not-rival pilots and you get to have three or so boss fights against. It's so strange that they couldn't even bother rotating the mechs or characters in the campaign since that seems like a sure given to actually spice that part up.
Besides that I have no qualms about the actual game itself. It's fun, it's short, it doesn't really overstay its welcome and if I had an issue is that some bosses are a bit of a damage sponge and that the ranking system doesn't make much sense especially when you're never really aware what about your ranking didn't net you an S-rank, and it seems to unlock fuck all. I'd recommend a pirate if you have a few hours to waste.