Nice work! I enjoyed the game, thank you!
Great job on making the game's rules clear without any written instructions!
If you continue working on it, I would suggest you use some visual clues about the direction of the connections and use the same color for vertical and horizontal connections because the orange color suggested to me, that something about the vertical connections was wrong.
Also the ability to undo the last connection would be great (maybe by right clicking on the last connection? You could make this discoverable by some mouse over clue)