It's in Early Access, it's in Beta, call it what you will. The version of Mercenary Kings you can play right now is still loads of fun and seems feature complete enough for me to relate what I've experienced during my playtime with it. At it's core, MK is a mash-up of Borderlands, Metal Slug and Monster Hunter. The shooting is of the 2d sidescrolling variety, you have a ton of gun parts to customize your weapon with and you can capture enemies and killed monsters drop materials. It's not perfect, but it's not officially out yet.
So far, my biggest problem I have with this game is how tough to play it is on a keyboard. They use too many keys, WASD for movement, IJKL for shooting, knifing, rolling, jumping, ZXCV to change your equipped thing and the Spacebar to reload. Even if this game was meant to be played with a controller, why not try and streamline the controls? I'd love if the reload button was the same as the shoot button because this game has active reloads - you press at the right time, you reload faster - after a while I've gotten used to it, but at first I was confused by the controls. Even now I fumble around menus trying to select things but cancelling for some reason.
Customizing your stock, barrel, scope, magazine, receiver and ammo type, you can craft the gun you want. If you have enough percentage of a certain gun type - shotguns, piercing guns, magnums - your gun can fire bullets of that type. Everything is about trade-offs, you won't get an automatic shotgun and the more ammo you can carry, the less damage you deal. Money isn't a big issue but materials throttle the speed at which you can craft your gear.
You get new weapon and knife blueprints after going up in rank, I'm not sure if I like that because the first thing you do after going up in rank is going to see what you'll be able to craft for the next 10-14 missions, since you don't get new blueprints during gameplay, maybe you should get blueprints for finishing missions or finding them around instead?
There's enough variety in the mission structure, killing enemies, gathering materials, getting somewhere on the map, saving hostages or defeating huge bosses. You go through the same maps often but they change the enemy types from time to time to break up the monotony, I'm not really a fan of everything being timed, it's just stressful. And like in Monster Hunter, the bosses will just run away to another location after a while. If you die, you respawn in the last infirmary you visited and you have 3 lives per level. I wish the mission briefings were more clear. "Destroy 1 storage" doesn't tell me if I'll need C4 or hand grenades or only my gun to destroy it. Having to restart a level because you don't have C4 in your 2 free inventory slots is annoying.
You can also craft mods that improve some of your abilities and worsen others. One that I crafted very early on is improving the odds of enemies dropping more materials at the cost of getting overall less money. I'm sure it helped me so far, but the game doesn't surface any of that stuff. Why not have a little icon next to the item drops so I know what rarity they were? Why not have a list of enemies with their loot tables so I know what to kill if I want a certain item? Maybe in the next version, but I think that's missing from this game.
I really enjoyed my time with Mercenary Kings. It's RPG-y enough to get me interested, the gameplay is good, you can have a shotgun that fires a ton of little pellets in a huge cone while making mewing sounds, it's also pretty tough; upgrading your armor gives you a very little increase in hit points and huge bosses that take most of the space just ram into you if you're not careful. I don't know how far in I am and what's left to change or add in the final version, but when Mercenary Kings hits steam 'for real', I'll give it another shot, that's for sure!