Games are a series of interesting decisions. That’s one formulation. Being asked what x+y is with some graphics is not an interesting decision. Perhaps an interesting decision comes later, but I wasn’t interested and bounced.
One of the hard things to do when building a game is to figure out why it's fun. It's hard enough that, in general, most folks just remake another game that's already figured out the fun.
You're doing a math game, math gamified. Let's throw a choice in there.
Since you replied, here's one idea:
(1) present five numbers.
(2) You, the player, chose two numbers
(3) You perform an operation
(3.1) operation: add/subtract/multiply/divide, but perhaps exponentiation and modulo and lcm and factorize and whatever else. it's probably best to keep it simple.
(3.1.1) this can get random: what was the highest number last round? how many green letters are there on the screen?
(3.2) operations are tied to the special attacks,eg tier 1 attacks are add/subtract, tier 2 mult/div, and so on.
(4) you type in your answer
(5) if you type in an answer that's the correct result of an operation applied to two of the numbers, then you do the corresponding attack.
So it's not add these two numbers pass/fail. It's you decide what math you want to do, and can do, and can do in a time limit, and that achieves the effect you're looking for.
Context is everything. If I turned that in as a serious project at work, tell me all the ways it was less than perfect. If a 9 year old brings it to show and tell, you explain how much you liked the cool parts.
If my florist handed me a dead flower, I'd be irked. If a 4 year old hands me a dead flower saying "I picked this for you!", I'd tell them what a beautiful flower it was and how much I appreciated the nice thing they did for me.
A 9 year old isn't a 4 year old, but I think you get the gist.
I would also encourage the kid as much as possible, but I'd be doing them a disservice if I didn't also take the opportunity to teach them about the basics of keeping flowers alive in transit.
