Most code and all textures by Vanessa Ezekowitz.

Some code copied and modified from the game's default mods (especially 
doors) and ironzorg's flowers mod.

Licenses: 
* For the lua code, GPL. 
* For the door open/close sound, CC-By-SA 3.0 by Slanesh on freesound.org
* For the gate open/close sound, CC0, by j1987 on freesound.org
* For all images and everything else, WTFPL.