Hard mode takes some while to build. It also solves itself pretty easily. And you can get over 100% on higher Difficulties.

It does have a certain Charm to it once finished, just wish you'd have a better Ratio of Colors, so you don't end up with some leftovers. (But then it'd become even easier I guess). 

• thanks for adding sound options.
• i can't tell how well i'm doing. i wish there were some scoring system or percentage i had to reach in X amount of moves so this was more of a game and less of a toy
• i also can't figure out how to restart this game
• hard mode hangs for a very long time before starting. you should put some indication of loading