The cascading explosions are definitely fun!
My two cents:
the cascading explosions should be triggered by the player's shots. This would give the player more agency over the explosions. They feel pretty random as is. It would also create a nice dynamic where you want to shoot the asteroids when they are far away but dodge them when they are closer (or risk getting caught in the ensuing explosion).
I would add a secondary objective, like collecting gems that are released by the cascading explosions or something similar. This would give the player reason to weave into the asteroids instead of just avoiding them all. Or you could add points and score extra points for triggering longer and longer explosion cascades. This would give the player a reason to hold out for that perfectly timed shot that would cause a massive cascade of explosions.
Minor points:
The asteroids should effectively die as soon as the leave the screen. I got killed several times by explosions that happened off screen which never feels good for the player.
As cool as the explosions are, they are maybe a hair too big right now. Ok maybe several hairs. You could probably cut their size in half and they'd still be super cool to watch and yet the game would be much more playable. Perhaps consider adding asteroids of varying sizes that in turn produce explosions of various sizes.
Random thoughts:
Maybe try making the player bounce off of asteroids and only die if they are caught in an explosion. That would make the explosions more central, and getting bounced off an asteroid and sent into an explosion would make for a great 'oh no!' moment for the player.
Consider dropping scrolling motion and going straight asteroids: single screen, asteroids wrap around the edges, player spins and moves all around the screen. Although I'd be amazed if 'Asteroids with Cascading Explosions' hadn't been done already.
Question:
what do the little blue and yellow icons that fly by do? I couldn't seem to interact with them.
Well as others have said, you have a good concept here it'd be great to see you take it further. Great job! :)