Reviews are meant to criticize, and that is what I will do below. I do want to make note that I mostly enjoyed playing, and that this game has a lot of potential.
At times, this game had me pounding my head against the wall - but not for any reason a game should:
-Domino placement is very buggy - sometimes just the simple act of placing a domino will cause it to fall over and thus, I have to start over.
-I noticed while trying to create forked paths that the game has a tendency to ignore one or more of the paths, though they all perfectly symmetrically placed.
-Sometimes, the finger pops out and, while attempting to place a new domino, instead knocks one over before the path is complete. I recommend a separate "begin domino effect" button to give the user better control over when Dominoes are knocked over.
-After placing several dominoes, I sometimes forget where the beginning and end of my path lie (in Free Form mode). You might include a directional indicator to show, before a domino is knocked over, which direction the path will run. Not so much an issue in Arcade mode ;)
-Also, on several occasions, pressing "Clear" somehow locks the mouse out - I had to right click to bring the mouse back into focus to place more dominoes.
-Additionally, "Undo" button appears absolutely worthless, as clicking it does not undo any made move.
-The single music track gets very old very fast; kudos for the mute button.
I am aware how difficult a work of this nature is to create. Though I still feel I'm being harsh giving only an overall 7, I can see you have put quite a lot of time into this. However, the problems above prevent me from actually giving any higher. If you fix these items, I would consider this worthy of a 9 or a 10.
Oh, and I'm voting 4 on the 5-point portal scale.