You might easily mistake it with the DS homebrew Earth Invaders, given that they are made by the same person, but, Earth Invaders 0: Before the Attack is homebrew made for the PSP and is smealum's entry to the Neoflash Summer Coding Contest.
He apologizes for not yet coming out with a polished version of the game, because he unfortunately lost a lot of his initial work when the source file of the game got corrupted. Good thing he's a regular Mr. Brightside and sees this as an opportunity to make improvements in the game. Our main concern, and I think everyone will agree, is to have enemies that aren't our clones. Also, while playing the game, I fell through the obstacles and never surfaced - literally. I was actually waiting for the game to end, since I assumed that I've already died, but it's just not doing that. However, even if it's still unfinished, there are already a lot of things that you can do. Over here at QJ, we got a kick out of watching Gotenks get his Ki back. The opening sequence is also worth a mention.
EI 002EI 003
Here's more of smealum's post about his entry:
That's why i'm presenting to you this incomplete version, i would like advices and i'd also like to know what things you like, don't like, or would like to have in the next version.
Also, none of the graphics (except the menu and the video....that i didn't finish actually, this is only a test video i made to test my "video player"....) are by me, i took the sprites from Dragon Ball : Hyper Dimension (SNES, 1994). You'll notice that the enemies look a little bit like you.... Undecided It won't be like this in the real version. Also, the "story mode" in this version is only the map browser...
You'll also notice a map creator, which isn't in its final version either - though it already works pretty well.
He's also made a map editor for Earth Invaders 0, it has a source code that permits you to load maps from external files. So you can not only edit and maps to EI 0, but do the same for your other PSP games as well. Here's the source code and further instructions from smealum: