The combos felt really good when they went off, even without the sound (though sound would have amplified it even more!). It took me a while to figure out that I need to hit multiple enemies to get the combo going (even though you said that in the description -- I clearly didn't read that carefully enough!), but once I did, it felt good to scale it up.

The knights were by far the worst enemy, since they were not only more targetted, but also moved much faster. Also, I would have liked some variation over time. I wonder if having some pieces that moved independently of the player would add some; e.g. have bishops that spawn on a random location and then just move diagonally until they hit a side and then bounce off, repeat.

Unfortunate you had to cut out sounds due to time constraints, I can imagine the combos being even more satisfying with audio feedback