Neat idea. I really liked the way that pieces move, rotate, flip and wobble through the movement and combos. I think the hit stop and vfx make the combat really pop.
After a few minutes, I did find that I was able to button mash my way through most fights. You definitely get hit sometimes, but you also heal enough to where you don't have to think much about defensive play. My suggestion would be to look at games that encourage a switch off between offensive and defensive play, like Furi, Ruiner, Hollow Knight, Sekiro, Ghost of Tsushima. Defensive play can simply mean moving around more rather than spamming attack, or it can mean running away from the fight / blocking / hiding.
It would also be awesome to have some kind of super duper slo mo mode where you build up a meter and then use the meter to make all enemies move in slo mo and allow you to zip around the battlefield and demolish every enemy.
I was kind of hoping that there would be some crossover between the combat gameplay and actual chess, not just in visual design. I think you did a phenomenal job on the combat for a game jam though, regardless of my criticisms I did really enjoy my playthrough.