Hi!
As an avid tetris player I was quite excited to play a 'simple' block connecting game - and your idea of slowly increasing the shape size was a really good one! I was a little disappointed that they didn't go past size 4 though - pushing it to go to 5 or 6 would have made it much more different from tetris!
It is a little glitchy - blocks close to each other sometimes start constantly switching colours, blocks sometimes 'fall down' from their position into empty spots below and reaching the red line doesn't reset your shape size or score (although that one might be on purpose). I have recently made a match-3 type game of my own though, which uses a similar algorhitm to determine where your blocks are and if they make 'matches' or lines, so I know that it is more complicated to do perfectly than it may seem.
Next time, try putting in some background music (even if it isn't original music!), it takes very little time but elevates any game to the next level!
Keep it up!