Input | Citadel docs

players.on_click(function(player, hit) end) -> connection

hit.button = "left" | "right": left is attack / swing, right is interact / use
hit.entity = display | hitbox | npc | puppet | nil: the thing itself, so hit.entity == dealer works
hit.entity_id = number?: its raw id; all there is for a screen's own frames, and for anything the script no longer keeps a handle to
hit.player = player?: another player, when that is what was clicked: a hit in a game
hit.block: = vec3? the block, when the click hit one
hit.face: = "up" | "down" | "north" | "south" | "west" | "east" | nil

players.on_sneak(function(player, down) end) -> connection

once per press and release

players.on_slot(function(player, slot) end) -> connection

hotbar 1..9

players.on_chat(function(player, text) end) -> connection

return false and the line is not said

player.rotation

{ yaw, pitch } in degrees, live; read only

player.sneaking

boolean, live

player.input

{ forward, sideways, jump, sneak, sprint, attack }: the keys held right now attack is the left button held on a block in reach: a client reports a held left button only while it digs, so it is false on air, and an adventure client never digs. A held left button on anything is: survival, player.reach long enough for the crosshair to land, and player:effect("mining_fatigue", { level = 5 }) so no block cracks forward is 1, 0 or -1 (W and S); sideways is 1 for left, -1 for right (A and D); the rest are booleans

player:ride(thing) -> boolean

sit on a display, a model, a hitbox or an npc, and go where it goes; false when somebody sits in that seat of a model

player:dismount()

get off; sneaking does the same, as off a horse

player.riding

boolean, live

player:look() -> vec3

unit vector the player faces

player:set_slot(n)

selects hotbar slot 1..9

One click is one event.
A held button repeats every 200 ms. That is not a click.
A left click on the world carries the block under the crosshair, up to five blocks from the eyes.
On a pack server, a click never changes the world.

The first players.on_chat takes over chat in its room. Each line is then said once as <name> text, unless a listener returns false. With several packs, each gets every line; it is still said once or not at all.