Cool game. Reminds me of Astrodle but with rounds.
Just a heads-up, the game lags a fair amount when spawning a lot of lightning bolts. This is in the web version. My guess is you either need an object pool for the bolts, or improve the way the targets for the bolts are determined. Maybe space out the chains over multiple frames.
I have to say the same thing I say about all Nodebuster clones. I wish the rounds weren't there. They force an otherwise satisfying gameplay loop of destroying asteroids and buying upgrades into a really rigid structure. One of the great things about incremental games and games with lots of upgrades in general, is that you can see the upgrades pop from too expensive to affordable as you're gaining money. That's not possible with rounds and a separate screen for the upgrade tree. Most people love the format though, so I guess that's just me.
At least the upgrade tree is more legible than in other Nodebuster clones, with nice big text and good contrast. Good design on the icons too, giving them a different shape after purchasing. And no tiers is also good. Finally, not having to play 3 rounds to buy one upgrade is nice, definitely keep that.
I like the asteroid types, keeps the game fresh. It would make more sense if the radioactive asteroids did damage in an area around them before being destroyed, instead of leaving a cloud after destroying them. It would also differentiate them more from the lightning asteroids.
Adding a visual effect to critical hits would make them feel more impactful. Also an idea for an upgrade: have the black hole emit beams every time an asteroid enters it, a bit like hawking radiation.
I beat the game in about 30 minutes, using all the upgrades. Overall really well done.