Arith / brain training

When I was in elementary school, looking at the car license plate
"I wonder if I can somehow calculate 0-9 using these numbers and symbols."
And I used to do that.

Now that I'm an adult, I thought it would be nice if there was a brain training app that I could play like that.

You can play in 4 difficulty levels.
・Easy
"Let's play with 3-digit numbers!"

・Normal
"Let's play with 4-digit numbers!"

・Hard
"Let's play with 5-digit numbers!"

・Very Hard
A super difficult mode with a 5-digit number!
Let's calculate everything from 0 to 29.

It's surprisingly difficult, so please give it a try.