I’ve learned lots of things from people who took the time to write interesting tutorials. This section is my mean to return the favor.
Most of these tutorials are for the Haxe language, but they should be pretty easy to adapt to your own needs. Haxe is the cool language that made real cross-platform development possible (using frameworks like OpenFL, Stencyl, HaxePunk, Flixel…).
800px-Bresenham.svg Bresenham magic: raycasting, line of sight…

Bresenham line algorithm is a quite simple tool yet extremely useful in many situations!

gameEngine02.jpg A simple platformer engine (part 2): collisions

Learn to write a lightweight and simple collision system for all your needs.

Last Breath A simple platformer engine (part 1): basics

A very short and simple grid based 2D engine which isn’t tied to any framework or platform.

Appy 1000mg Beveled pixel : howto

A quick explanation of the “beveled filter” I use in many games.