This is a great concept that feels like it's about 80% there. Some suggestions if the author is here/reading:

1. I badly want the ability to rotate pieces. Perhaps it's too strong to have this universally, but maybe i get 1-3 piece rotations recharged on each Reroll?

2. Having multiple of the same orientation piece isn't great, but a few times i got 3 pieces in identical orientations. This is really fun-sucking and i'd either code that case out or weight it to be very unlikely.

3. UX-wise it would be great to be able to hold my mouse down and drag across pieces to highlight them instead of needing to click on each block individually.

Feedback aside, i really love the concept here and think it's a great first pass. Some UX improvements i think could make this a really addicting game. Awesome job.