Gameboy ASM (Z80) tutorial - http://gameboy.mongenel.com/dmg/lesson1.html
Errors using yellow sprites in pokered - https://hax.iimarck.us/post/36245/
Modifying maps - https://www.youtube.com/watch?v=tzr4Od68Gb0 https://github.com/huderlem/RBMap
General tips - http://pokemonhackersonline.com/showthread.php?t=15237