A nifty little run'n'gun game that begs to be in 2D. Or with a less perspective distortion in its 3D camera.
But let's start from the beginning.
Giant mechas attacked the world and make short work of the military. You, as the best of what's left (game's own words), are tasked to destroy those mechas. You have a standard machinegun to take out vulnerable parts and a hammer to bash the mechas' core once uncovered.
The standard gun can be aimed all in 360 with the analog stick, although it snaps to the standard eight directions; with enough finesse you can aim it everywhere though. The jump is very generous and floaty, and the shoulder buttons allow to fire without moving; the same buttons are used to cling onto walls once you receive the appropriate powerup.
As you destroy mechas, or better mechsterminate enemies, you collect coins to buy extra health and additional weapons.

All stages feature a single giant robot and you can think of them as self-contained boss fights. Mech design is very inventive, and often when you think you're done with a mecha, you have to face an unexpected extra phase. Depending on the attack you either take full or half damage, health pickups are somewhat rare and all pickups are on a very brief countdown, in some cases you won't be able to collect coins or health because the enemy mecha is going through a pattern that physically blocks you from reaching them. It's not a particularly bad thing however, between the stage completion bonus and all the times you'll retry a mecha you never really have to grind for anything. Everything can be mechsterminated with the standard gun, and in fact I've only used that because it's a very versatile weapon good for all situations.

To expand my opening statement, controls work well but at times your character ails to latch onto surfaces, and I think this is partially due to the camera swinging around the battlefield, chaing perspective and thus making you misjudge distances. The camera in Umihara Kawase Fresh! is similar, but the main difference is that Umihara there latches to the edge nearest to the screen, while in Mechstermination Force your character is in the center of useable space.
It's kinda hard to explain, but you just need to play MF once to understand it. Also controls aren't as tight as I'd wish, during evry fight I had the impression I could have avoided hits if the jump wasn't so floaty and controls via the analog stick so loose. Inputs via d-pad are more precise, but you lose the ability to aim the game everywhere.

One thing I love is that Mechstermination Force doesn't have loading times, if not a one/two seconds log balck screens between the main hub and any fight. Even restarting a stage is instantaneous, a definite plus.
Small camera woes aside, graphics are easy to read at any zoom level although some fights do throw a lot of things at you, and some patterns are hard to avoid the first time.

Mechstermination Force doesn't look like a very long game, most fights take less than 5 minutes, but you can achieve up to three stars based on how long you took to mechsterminate an enemy, and the three-star ratings are incredibly demanding.