Finicky controls are a cornerstone of most twin-stick shooters. In this case as with many others, you control the mech with one analog stick, and shoot in whatever direction you like with the other analog stick. As a general rule, it’s hard to get any more complicated than that. Unless you’re Gatling Gears and you feel an element of Shoot ‘em up should be included.
What do I mean by “element of shoot ‘em up?” Well, you know those games like R*type where you fly into a barrage of enemy gunfire and have to avoid torpedoes, missiles, obstacles, and enemies? "Bullet Hell?" Gatling Gears kind of did that. During any of the larger battles, the screen will be largely littered with torpedoes, enemies, flamethrowers, etc - so you really have to pay attention to where your mech is as well as being able to aim at the enemies that swarm from all over the screen.
This tactic is an awesome challenge at the beginning of the game when there aren’t too many enemies, but quickly becomes frustrating as time goes on. In co-op it should also be noted that the difficulty of the game scales slightly by adding additional enemies (and more torpedoes and such to run in to) with two players.
As you progress through the game you have a score, partially to compare your progress with your partner, but also to unlock things at the end of each section. Gears are your primary source of points, and picking them up from downed enemies is important. Being the one to shoot down enemies also adds to your score, so go ahead and be a screen hog to boost the score.
At the end of each level, that score is compiled into EXP for your group (you still have your score ranking, but the EXP is shared). As you gain EXP, the game unlocks extras for you. These extras are not useful things like power or speed, but rather quirky things like a pet to follow you around, effects to add to your mech (like shooting leaves out of your gun barrels along with bullets), or skins to change the way your mech looks.
You’ll also pick up “gold” to buy upgrades, which are the important things. Most levels had 3 pieces of gold to buy upgrades, and fortunately it’s not a race to see who gets there first for the gold. Gold is shared between both players when one player picks it up. The only thing you really have to race for are gears and power-ups.
When you buy upgrades you can get: Increased gatling gun firepower, better rockets, improved grenades, or health increases. Fortunately, you can also sell back (downgrade) those upgrades so you can change your mind later on if you need to, just so long as you can find the pirate ship shop thing.
The power-ups were handy, but didn’t seem to last long enough. Power-ups are things like a Gatling gun booster that gives you increased firepower for a few seconds, or rocket/grenade booster. The firepower from these power-ups was drastically improved, but the duration was based on a timer, not on use.
In order to get the most out of your power-ups, I feel like the duration based on overall use so you can manually reserve it for those big waves, rather than just running out while you’re waiting for more enemies to appear would be more effective. Either way, they’re a fun experiment in carnage while they last.
When you’re out of power-ups and it’s looking grim, the one savior to you is a health item - but those don’t necessarily do enough some of the time. Your health bar can take quite a beating quickly, and you only get 3 lives (well, technically 2 - but the 0 life counts as well). The lives are not shared, which is a relief, but if one person isn’t doing so well and they lose that last bit of the 0 health bar, the level is over and you lose as a team.
Being careful in such a hectic environment takes some skill, and patience on behalf of your co-op partner. It’s tough to say if the storyline (5 chapters plus an extensive prologue) are worth while to you, but maybe you’re the survival mode type.