* Called when a button is pressed in player's inventory form
* Newest functions are called first
* If function returns `true`, remaining functions are not called
+* `minetest.register_on_dignode(func(pos, node))`
+ * Called when a player digs a node
+ * Newest functions are called first
+ * If any function returns true, the node isn't dug
### Sounds
* `minetest.sound_play(spec, parameters)`: returns a handle
* `spec` is a `SimpleSoundSpec`