Played web version
-Main Menu is cool, I like the color switch per option.
-Starting with classic mode, puzzle concept is pretty cool, focus on chaining square areas and not just lines/total connected blocks. I like how it takes time to clear areas, so if you're quick you can keep adding blocks to increase the timer+size of it. Holding a direction goes way too fast, as soon as the echo events kick in it may as well already be on the other side of the arena.
-Game freezes when going over the fill limit, which looks bad. I also thought that it crashed due to that, but no pressing esc/enter will fix it. Also, the loading after selecting a mode is about 3-4 seconds, it's a bit long and probably needs a loading screen even though it feels like this game shouldn't have load times like that.
-DigDown is a good alt mode, it's a different focus but also helps train the player for dealing with messy situations if they come up in classic or one of the other modes.
Looks like a good base to build on.