At the moment there is a lock function that gets called only when the player has stopped trying to move the piece for a set amount of time.
I could definitely look at adding a second condition to prevent exploiting that and I agree it's worth considering.
Then again, I'm considering a hard mode that unlocks after you register a certain minimum score.
In hard mode I'd probably remove this "slide" feature altogether.
Something to ponder over the next week.
Glad you had fun :)