I played for a bit and I have a few comments:
At first I thought the backspace button was a button to return the main menu.
It'd be nice if you could deselect letters by pressing their button again, or clear to a specific point by pressing on that letter of the word.
It'd also be nice if the selected letters were a bit more distinguishable from the unselected letters, like if they actually moved with the button graphic and/or faded a bit, or if the button colour changed slightly.
The counters at the top don't seem to be ticking up for me as I complete words. I'm not sure if that's intended or not.