Just to summarize some improvements from others I've seen and agreed with: Max board symbol, coin on/off option, board rearrange tool, board sell option, and poop board doesn't seem worth any investment.
Awesome game though!
Upgrade and purchase costs are absurd for the amount gained each run, even given longer runs. I really do hope the devs listen to this criticism that's been echoed over and over. Would be 5/5 for me otherwise.
Game needs DEVELOPER SUPPORT. Just like so many other games in the same genre, build user support by supporting the users. You make a great game, with some significant flaws, and several easily improvable aspects that wouldn't take that much time to fix. Yet there is never any dedicated developer support, make a game and move on to the next is kind of a trashy way of doing business.