Hi Maelstrom, finally got around to trying this game. Not bad!
Around level 50, I actually started taking damage, and for a moment the game was right in the "sweet spot." Meaning, under pressure, but possible to overcome. After going backwards a little I managed to get one more level to 51.
The problem is before and after that beautiful moment, the game was sort of "decided." Again there is a clear better choice with the upgrades: earth every time. There's just not enough pressure at the beginning to make any difference. And once you get the laser, forget it - I was struggling to find enemies before they were automatically vaporized.
Then once I survived long enough, the enemies became overwhelming and the upgrades were long dry. I did not have the radar again, but it was clear that there were just too many ships for all my firepower.
It was right in the groove for a short time, so I think that could be extended to the rest of the game with better balancing. More pressure to start, and more upgrades once it gets really crazy. Also the ship is -real- slippery, which didn't matter all that much since you can't crash, but you might want to try out more "traditional" movement (we could assume the ship has auto-braking thrusters). Or maybe limiting the player's top speed.
On a non-gameplay note, the window was way too big for my screen. Still playable but it would help to have the choice to resize!