Secret Maryo Chronicles is a 2D Jump&Run Game built upon SDL. It is open-source software so the source is included in the download package from Sourceforge.
Anyone who played games back in the day of the SNES will recognize just about everything in this game except maybe for the added extra of a level editor. Activated by F8 in the game, you can insert any graphic file as a background or massive sprite in the game. Many standard graphics like hedges and ground sprites are included. You can insert enemies, set the player's start position on the level, insert active sprites, and create semi-solid sprites which the player can jump through, but can not fall through.