Nice game, needs a few more things
-the sliding physics (not the speed but that they slide down)
-the heart move (but I think it might be broken)
-Add music, at least sounds... comon
-make the sliding faster, maybe 2-3times faster
-DO NOT ALLOW THE HEART TO BE USED ON GREYS (this might be a bug), so I just drop a few rocks and use the heart on a grey and I win (looked again apparently this is a lose, how about giving players an error message if they attempt to use a heart on a grey box. as no matter what in that version there will always be a color on top to choose from)
-SIGNIFICANTLY reduce the frequency a player gets a grey block in grey mode, its a pain in the ass because you would get a red, 3 greys, blue, 3 greys, red, 2 greys. See what I mean.
-I played grey mode and I got a gameover when I hit one of the darker ones. Did I win? or lose. I dont know. Instead of "game over" have a "congratulations" if you win. (just checked instructions apparently that was a lose. Maybe have them fixed and only fixed, such as you can't 'remove' them)
-Have a color endurance mode. Around the same time you get a heart, the grey blocks move up 2-3 levels.
-You never gave what exactly constitute as a "win," you really only said what is a lot
-Show us the next block color (or 2-3 block colors would be better)
if two blocks drop at the same hieght towards each other then they make a square hole (thats fine). However, if I put something in the gap above the two boxes and than get rid of one of two original blocks, the block in the gap above flies. (thats not fine)