From the blog "Sandbox Update Notes"
+ Added Chests
+ Added Lava
+ Added Hammer - Primary tool for building, will replace direct building entirely in the future
+ Added Lemon
+ Added Dirt
+ Added Stone
+ Added Wood
+ Added /setspawn command (not yet functional)
+ Added interaction hints - used to display useful hints next to cursor when highlighting over certain objects
+ Added footstep sounds for most tiles
+ Added rain sounds
+ Added underground world type, with several world features
+ Added several playe