If you were playing on normal, the first boss actually gets buffed with 3 more skills after you die to a later boss, so that's probably why it seemed like the coins didn't show up. I actually balanced the game with the goal of there almost always being a black slice on the board because I actually hate waiting too long for openings in games (lol). Technically it wouldn't be unfair to make the player wait, since there's no consequences to waiting, but I decided to retain the current speed after stopping and guaranteeing board changes in the player's favor to minimize wait times to keep the fast pace of the game.
The ASDF abilities are more geared towards playing not on max speed and going more for consistency, where it's useful to drop the speed back down after resetting the minimum speed if you accidentally wait too long, and flipping the board for better openings on the second boss, so it's for accommodating different playstyles... and also I didn't know what to put there so bam, skill panel. I think it's a somewhat different experience to go for consistency instead of going all in, so maybe give it a try if you want.
I'm pretty glad to hear you enjoyed the game! It's my first time doing so many animations in the actual game engine- usually I'd just go for frame-by-frame animation, so it's good to hear that people like it.