The timer adds a very interesting tactical twist, as you now sometimes can wait for the timer to end so you can complete the line above that and just occasional try not to complete certain lines. Timing well and planning adds an extra layer of strategy to a classic.
Job well done!
Graphics are a bit simple but work well. The grey "preview" could be a bit darker, when thinking fast, my mind was getting confused and thinking the real block is almost at the bottom and I need to act fast.