Small World Attackers!
It's not quite Space Invaders... get it? Play Small World Attackers! here

Anyway, what started out as a 3D-with-a-twist version of a Space Invaders clone (the twist being distinct first-person and third-person views) turned out in a more fun arcade game than I imagined. While working on adding the "occasional space ship" fly-by, I found the challenge of locating and shooting it more fun than the regular aliens. So, I made that the primary gameplay and moved the invaders to a "classic mode" option.
The interesting mechanic is really about the use of the swapping between views (TAB key).

So where in past Ludum Dares I went for more complex mechanics, I went for a simple clone type of game - but with more time to play test I found some interesting hidden gameplay. Overall I'm pretty pleased with the entry, mostly I just took a different route than usual and it worked fairly well I think. As usual some tweaking of point system and how fast things speed up and get more difficult could help. But if you play for a few minutes you should see the ramping up of difficulty fairly fast.
Enjoy and please leave a comment!
https://ldjam.com/events/ludum-dare/38/small-world-attackers