Mathrax originated on the German puzzle website janko.at. Fill in numbers from 1 to 7, such that no row or column contains any duplicate numbers. Sounds pretty normal so far, right? Now let’s add math!

The German puzzle Miss Lupun (an anagram of “plus minus”) was the inspiration for today’s puzzle – Math Ladders. Simply change the number at the top of the building into the number at the bottom using the mathematical operations in the circles between floors. Use only the digits 0-9 in four separate columns.

Gokigen Naname, commonly shortened to just Gokigen, is a line placement puzzle. Place a slanted line into each cell, following numbered clues at grid intersections.

Shade four cells in each region to place exactly one L, I, T, or S-tetromino there. Shaded cells form one orthogonally contiguous area.

Shikaku is a popular area division game, often used to teach about the area of rectangles. Divide the grid into a series of rectangles. Each rectangle must contain one and only one number.