I noticed that students were spam-answering puzzles, and so I put in a freeze effect when the answer is wrong. The tile will thaw out, but it takes a few seconds.
I think this is a good enough of a nudge so more students will solve the puzzle by using and developing their number sense rather than just spamming answers.
I also put a time stamp at the end. Some students were showing me the same victory screen multiple times to get multiple prizes.
I also added another stage, bringing it to 12. If I can think of 6 more, I'll switch to levels and stages.



