Scratch

Here are my ideas:

1). Multiple weapons like a blaster, a cannon, ect...

2). Money to spend on upgrades.

3). Ships ocassionoly drop power-ups.

4). A huge boss battle.

I hope that you like my ideas!

You are on a spaceship, then youre shot down so you have to go and find pieces on the ground to rebuild, or maybe you have missions - which require you to fly your craft there, land it, complete the mission, and then return to base in the spaceship.

when gf clicked
repeat until <(know how to put that underline thing with a message) = [TRUE]>
  say [how do you put that underline thing with a message?]
end

Think about the old space adventure games like Starflight and Star Control 2. They had two-dimensional space. This is good game design, since the 2d space is easier to navigate and visualize and has a larger density of interesting stuff. But then you land on planets, and they're a whole another two-dimensional surface. There's always a weird jump from space to planet. Why not stay consistent, and make the planet surfaces one-dimensional? Flying in the atmosphere would then look and feel like Gravitar or Sopwith. Landing and moving on ground would feel like a platformer.
You'd need a good rotation support in the graphics engine, as whenever you move close to a gravity source the screen should rotate so that the gravity well is down. You could do all sorts of interesting stuff with big and small planets, asteroids, space stations and the insides of space ships if you were consistent with the idea that you only have 2 dimensions to work with. Though I'm not thinking about something utterly surreal like a flatland universe, I'd go for the platform game route and keep the basic game elements like humans and vehicles pretty much recognizable.