Interesting game beebster. Design is very unique and fresh take on the space shooter. I found it quite tough and did get to Ludicrous mode, which certainly surprised me a little. I love the graphics and sound. I enjoyed playing it.
The only tweak I would suggest is that hitting the planets or enemies feels more like luck than skill, but more satisfying if a bit more skill is needed. Perhaps the movements could be a bit less random and follow a pattern so you can think ahead. I can see that you don't want it to be too predictable either, else it would get easy after a couple of playthroughs.
Great work and interesting to see an SDL game.