Logical deductions are what you need to solve Hexologic's number-based puzzles. In its increasingly tricky challenges, you must fill in its hexagonal grids with the right numbers in the right places, a task harder than it sounds.

Each stage in Hexologic is crafted from connected hexagons, with numbers at the ends of rows; you need to place dots within those hexagons so they add up to the numbers. The headscratching comes from the fact that dots can interact along multiple diagonals, so figuring how where to place the correct number of dots without messing up sums horizontally or vertically can become a test of planning steps ahead. Hexologic gradually introduces new mechanics throughout its 60-plus levels, such as hexs that affect adjacent ones when manipulated. 

While the central stages let you solve them at your own relaxed pace, additional timed challenges introduce a sense of urgency to truly test you mental math skills. Hexologic is available for $0.99 on the App Store and Google Play.