Pretty good
Couple things I would change:
First of all, it doesn't have enough in the way of a curve in the prices of upgrades, and it ends up with the beginning upgrades costing too much to get without playing 10 rounds and the ending upgrades obtainable very easily. \
Second, I'm upset by the absence of things in space. Not a gameplay issue, it's just hard to gauge how far you sent someone flying when there's nothing to compare it with but a number.
Third, there are a few spelling errors. Should say "secs" instead of "segs", for one. I would also like to see the numbers on the power meter reversed, because right now it looks like an improper fraction with the cap on the left and the current power on the right.
Other than that, gameplay's great. Keep up the good work.