Math

From: http://mathoverflow.net/questions/8846/proofs-without-words-closed

Euclidean Algorithm (finding greatest common divisor of two numbers, GCD)

The realization here is that if a GCD must divide two numbers, then it must divide each of the sides of a rectangle whose dimensions is given by the numbers.

Therefore, GCD(16,38) = 2.

- Pants Party Trick -- invert your pants inside-out without taking them off

Hexagon Grid Coordinate System

http://www.redblobgames.com/grids/hexagons/

http://www-cs-students.stanford.edu/~amitp/Articles/Hexagon2.html

A hexagonal grid is a projection of a cube-grid.

Ugly way to model hexagon grid

3-coordinate way to model hexagon, x + y + z = 0

2-coordinate system, z = -(x+y), z is implied

http://stackoverflow.com/questions/2049196/generating-triangular-hexagonal-coordinates-xyz

http://stackoverflow.com/questions/2459402/hexagonal-grid-coordinates-to-pixel-coordinates

Trachtenberg Computation System

Youtube: https://www.youtube.com/watch?list=PLjvCUQASvwjlSVr4530VoSgItXy9b3Kux&v=XAcwPJq6dPM

Book on Amazon: http://www.amazon.com/gp/product/B006WB7R4I

Derivation of the Rules: https://en.wikibooks.org/wiki/Trachtenberg_system

Russian (read online): http://padaread.com/?book=32984&pg=7

Russian (download the book): http://www.read.in.ua/book138182/