I've been seeing a lot of comparisons of Iji to the Metroid games, which I guess is tempting due to the female lead and the sci-fi setting, but really the similarities to Metroid end there. The game incorporates some of the statistical and level-up concepts of System Shock 2 into a 2D platformer, but the minimalist graphics and the gameplay actually remind me more of classic rotoscoped action games like Out Of This World and Flashback. Just, y'know, without the rotoscoping.
So, we're on Earth, it is the Future, some young girl and her brother are visiting their Dad at his super science research facility, when suddenly the sky darkens and the Earth is invaded by a fleet of alien spacecraft. Six months later, only a handful of survivors remain in the depths of the research facility, trapped in by alien occupiers. They manage to outfit the girl with cybernetic implants, however, in the hopes that she can bust her way out of there and convince (somehow) the alien occupiers to take off. A long shot, but it's all the hope they've got ... and of course, you'll be playing the role of the girl, otherwise known as the titular Iji.
The weakest part of Iji, unfortunately, is the first few minutes. It has both a more complex ongoing story and a more sophisticated gameplay system than the average run-and-gun game, which are good things, but to get you acquainted with them it does a whole bunch of "telling" (in the form of dumping tons of text boxes on you one after the other) rather than gradual "showing". Players impatient for The Action will likely start skipping these due to the sheer amount of them, and thus may miss some important concept needed later in the game, hampering further enjoyment.
Grind it out past the first level (you can save between each level), however, and you are pretty much in the clear. This is where the game really picks up, and continues to both introduce new gameplay elements and new twists in the ongoing story with each new level. The basic gameplay is actually a bit reminiscent of Rolling Thunder, along with the design of the main bulk of enemies that you face. Iji cannot shoot while jumping or ducking, so you have to be careful in your approach to enemies. Her basic roster of moves is a kick that can break crates and break down doors, the ability to switch between different types of guns she finds, and the ability to hack security doors and locked containers that she comes across. You get a limited amount of potential experience per level, and choose what stats you want to upgrade. In addition to firefighting it out with the enemies by stealing their weapons and learning how to use them, you can also "hack" them if you sneak up behind them, which can do everything from making them explode to making them go haywire.
The games gives you the option of playing as a "pacifist", which changes the story somewhat as you go. However, this mode was kind of implemented poorly. Due to the structure of the levels, and the fact that every enemy immediately opens fire on you with high-powered weaponry the second they see you, "pacifism" amounts to "willingly getting shot without retaliating a bunch of times and hoping you don't die" for the most part. You can kick enemies to stun them (sometimes; the larger ones you face with increasing frequency as the levels go on usually can't be stunned), and you can sometimes sneak behind them to hack them, but hacking is very unpredictable and often ends up damaging you when the enemies self-destruct. It isn't like Metal Gear Solid where routes of avoiding conflict were actively built into the design. Really, the "pacifist" mode seems silly when the game obviously puts such an emphasis on firepower and keeps throwing newer and bigger guns at you, almost like you're supposed to punish yourself by not doing what the designer clearly intended for you to do (you also have less and less moral impetus to engage in it as you proceed through the game and find out more and more what thorough assholes both the alien races in the game are.) The game never creates any palpable moral conflict in what you are doing; I had no qualms with wiping the hell out of any alien I saw, even before I found out all their Dark Secrets later in the game. If you try to do the pacifist thing, you'll probably just end up feeling like a sucker, but some people have managed to complete the game that way.
In spite of some minor flaws, I found it to be a really good time on the whole, and extremely impressive for a one-man enterprise in Game Maker. The accompanying digital soundtrack, a digitized combo of metal and chiptunes, is also pretty good and was actually worth probably the extra 20 MB it tacks onto the download. Any fan of sci-fi or run-and-gun games should be pleased with this one.