Ok, my game is almost complete, at least the main idea, interaction and elements required (graphics, sounds, gameplay, etc), during the last 3 hours I created the level system, an explosion animation (I didn't find an animation that suites my needs so I need to create it from scratch using gimp and imagination), I also added sounds.
In Addition, my tester (my 4 years old son) did a test and I think it worked as expected, everytime he see me on the computer ask to play the game again and again... the magic is done!
Now I need to work on the following things:
1. The health of the UFO
2. The health of the player
3. The fight back from the UFO (easy with the engine I created)
4. An score system.
5. More sounds.
At this rate I think I will finish my first game in 1 week (or less if I have time during my vacations).
I'm very happy with the current results and I will share some demos of the code (not the one used in the game, but I will manage to create some demos of how I used SDL in my first game).