Very cool! A couple things you could fix:
When the entered word exceeds the length of the insertion box, the insertion box becomes permanently stretched. You could make resetting the size of the insertion box part of the text entry so it goes back to its normal size each time.
Long entries overlap neighboring bingo board cells. You could maybe make the text size reduce based on how many lines it wraps into, or just make the text object scale down (although it will look weird).
Edit board/edit cell?
