first impression was pretty well. the first 5 runs were still fun. but than it got some kind of boring. getting just something about 150 buck/run was a bit disappointing compared to the prices. especially to the fact that EVERY upgrade cost increased after buying the first upgrade (at least the cost of the first 3 upgrades, the radar not included). The radar is a pretty nice idea and is well made, i like it. the enemy dropping from time to time ... if you add a "how to play" you should mention it in there. secrets and rewards for reaching a certain depth sounds cool. But make sure that these rewards are not essential for being able to further continue the game. There is nothing worth in such a game if you got stuck on a certain point because of the need of some kind of upgrade/bonus but not being able to afford it anyway. I could imagine something like a portal unlocking very 3^x meters reached (1,9,27,81,243, ...).
well, all in all, just keep going. looking forward the finished game.