SMILE is an editor for Super Metroid written by John “Jathys” Mathys. The latest stable version is 2.5.0. Jathys later worked on unofficial releases entitled Parlor with a major focus on building a more consistent user interface and bug fixes. A 3.0 version was even planned at some point, but the author eventually halted SMILE's development and made its source code public.
While there are several derivative versions of SMILE in the making, these guides cover the use of SMILE 2.50, as it is the latest stable release of SMILE.
These guides should cover things that should only be attempted once you have a good understanding of SMILE and at least a basic understanding of what hexadecimal is and how to use a hex editor .