The Challenge,,, The Point... The Incentive...
Where is it?
This is a great concept for what it is, and I enjoyed the first half of the first level.
Then I realized I was never going to die, and by level 2 I had max upgrades and the S icons I was receiving were the lives I'd never need.
In other words, by the second level your player is left feeling like there's nothing to keep them going. Why am I doing this? The first level is easy, thats cool. But the second level should be at least a step ahead, instead we're stuck with a copy/pasta of the difficulty with a couple different enemies.
The pace is also far too slow for a top-down shooter. Throw some diverse squadrons at me, and keep me on my toes. Push the stress, and don't be afraid to kill me.
This review is of course coming from someone who has played his fair share of Arcade games, so I can't speak for those who aren't used to this style of game.