Pyramidu - Math pyramid puzzle

Pyramidu: the Math pyramid puzzle

Pyramidu is a math puzzle game, where you fill the empty boxes in a pyramid with correct numbers at the correct positions.

The boxes in above are dependent on the boxes below them, in a way that two adjacent boxes have an operator between them and the box above them should hold the result of the operation involving the number in the boxes below and the operator between them.

The pyramids come in different sizes and complexity, giving the puzzle difficulty ranging from solving simple calculations to solving equations and systems of linear and nonlinear equations "but don't worry ;) you will solve them before you know what they are".