This is a game I made for my 8-year old who loves games, but doesn't like to practice math. In the game, the damage dealt to enemies is a result of calculations. This means that results which are harder to compute are more beneficial to the gameplay. I was surprised that he would estimate and compute hard ones first, because it meant beating the enemies in style.

Features:

explore the forest
fight monsters in turn-based combat
cast mathemagic spells
compute damage with addition and subtraction up to 200, and multiplication up to 100
find map scrolls to help you navigate the maze, or health upgrades to beat bosses
collect magic digits to build your numeric spells

Is it hard?

In the early game the enemies are weaker, and there's more room for error.
Later enemies have more HP and hit harder, but the player can still win with a couple of errors. Sometimes the battles can be won quickly, if the player gets lucky with digits chosen for calculations. For example, 98+98 does massive damage.
Bosses require precise computation. Even then, make sure you collect most of the health upgrades before attacking.

What's the Forest like?

The map is procedurally a generated maze - different every time you start a new game.
Monster and treasure placement is also randomised.
Sometimes you might get map upgrades at the very start, another time you might get health upgrades instead.
Order in which you gain the digits is also random. You might start with something easy as 2 and 6, and doing math like 26+2 or 62-2. Or you might get 8 or 9 quickly, which is more challenging, for example to compute: 83-38.