I just finished playing an awesome freeware platformer shooter named Iji.
It start is pretty typical - Earth gets invaded by Aliens and you have to fight them. Then the "typical" ends. The protagonist isn't exactly happy to have to kill them and the main theme of a lot of arcade shooters - killing tens or even hundreds of enemies and total war on Earth is treated seriously.
The protagonist is a cyborg girl and a lot of usual shooter gimmicks like carrying multiple weapons, "health" and "lives" are explained in-game with nanotechnology.

Anyone else played it?

Not played it myself, but I did run across its TV Tropes page (and from your title, I wonder if you did too...?), and mentally file it under 'look into this at some point'.

I haven't really been prioritising games recently, though, so (unless it's particularly short) I'm unlikely to play it any time soon... ^^

Nope. I didn't even know that it has its own article there :lol: . I watched a video about Top 10 freeware indie games and it was on first place.

It takes about 4.4-6 hours to finish. It's pretty well balanced, so it doesn't require much (or any?) repeating of levels while at the same time doesn't feel too easy.