Session Expressions Reference

Reading Session State

• flagName - Providing a flag name on its own checks if that flag is set, returning 1 if it is, 0 otherwise.
• !flagName - Inverts the logic for checking flags, returning 0 if the flag is set, 1 otherwise.
• #counterName - Reads the value of a Session Counter (integer) instead of a flag.
• @sliderName - Reads a Session Slider (floating-point number).

Types

Session Expressions can operate on many types of values:

• bool - True/False value, represented as 1 or 0.
• int - 32-bit integer value, e.g. 1, -123.
• float - 32-bit floating-point value, e.g. 1.312.
• string - UTF-16 text, e.g. "hello".
• Vector2 - A pair of 2 floats, available via .x and .y fields, e.g. $vec(3, 4)
• Entity - Represents a Celeste Entity object, e.g. $player.

Type Fields

More complex types have fields that can be accessed via obj.field syntax:

string

• .len - int - The length (in characters) of the string, e.g. "hello".len -> 5

Vector2

• .x - float - The position of the vector on the x-axis, e.g. $vec(3, 4).x -> 3
• .y - float - The position of the vector on the y-axis, e.g. $vec(3, 4).y -> 4
• .len - The length of the vector, calculated as $sqrt(x*x + y*y).
• .lenSq - The squared length of the vector, calculated as x*x + y*y. Faster to calculate than .len.

Entity

• .x - float - The position of the entity on the x-axis.
• .y - float - The position of the entity on the y-axis.
• .pos - Vector2 - The position of the entity.
• .sid - string - The SID (String ID, used in map editors) of the entity, e.g. FrostHelper/IceSpinner for Custom Spinners. Can be ? if the SID cannot be obtained for the given entity.

Commands

All commands start with $, and allow you to get access to various values, not just those coming from the session. Mods can add their own commands.

• $deathsHere - int - Returns how many times the player has died in this room, resets after a screen transition.
• $deaths - int - Returns how many times the player has died this session.
• $hasGolden - bool - Returns whether the player is carrying a golden berry. 1 if they are, 0 otherwise.
• $restartedFromGolden - bool - Returns 1 if the current session started due to a golden death.
• $coreMode - bool - Returns the current core mode: 0 if not set, 1 if hot, 2 if cold.
• $photosensitive - bool - Returns whether Photosensitive Mode is enabled. 1 if it is, 0 otherwise.
• $allowLightning, $allowScreenFlash, $allowGlitch, $allowDistort, $allowTextHighlight - bool - Checks the corresponding Everest-extended Photosensitive Mode settings.
• $dashes - int - Current player dash count.
• $maxDashes - int - Maximum allowed player dash count.
• $stamina - float - Current player stamina.
• $speed - Vector2 - Player's speed.
• $pi - float - The value of Pi.
• $e - float - The value of Euler's Number.
• $dtime - float - The delta time between frames, taking into account Assist Mode options.
• $player - Entity - The current player.

Input Commands

Buttons

To read vanilla buttons, you may use any of these Commands:

• $input.esc, $input.pause
• $input.menuLeft, $input.menuRight, $input.menuUp, $input.menuDown
• $input.menuConfirm, $input.menucancel, $input.menujournal
• $input.quickrestart
• $input.jump
• $input.dash
• $input.grab
• $input.talk
• $input.crouchDash - Demodash

Modded buttons can be read via $input.mod.modName.buttonName, for example $input.mod.MaxHelpingHand.ShowHints.

By default, these commands return 1 if the button is held, 0 if it isn't. If you wish to check for something else, you can add a suffix to the command:

• .check - default behavior.
• .pressed - Whether the button just got pressed.
• .released - Whether the button is not held.

For example, $input.grab.pressed checks if the player has just pressed the Grab button.

Directional Inputs

To read directional inputs, you can use these commands:

• $input.aim - Vector2 - used for dashing.
• $input.feather - Vector2 - used for flying in feathers.
• $input.mountainaim - Vector2 - used in the overworld.

These values are Vector2's containing floats in the range [-1, 1]. When playing on a controller, these might be non-integer values, but on keyboard, they will always be -1, 0 or 1. Make sure to keep this in mind, and check the sign of the values (using < 0 or > 0) in most cases.

For example $input.aim.y < 0 checks if the player is aiming downwards.

Functions

Functions can be called like $func(arg1, arg2, ...):

• $min(arg1, arg2, ...) - int/float - returns the smallest value from all provided arguments.
• $max(arg1, arg2, ...) - int/float - returns the largest value from all provided arguments.
• $clamp(x, min, max) - int/float - clamps the value of x so that its between min and max
• $abs(x) - int/float - Returns the absolute value of x
• $sin(x), $cos(x), $tan(x) - float - Calculates trigonometrical functions, x is assumed to be in radians. (Tip: $pi)
• $pow(x, y) - float - x raised to the power of y
• $pow2(x) - float - x raised to the power of 2
• $sqrt(x) - float - square root of x
• $cbrt(x) - float - cube root of x
• $exp(x) - float - e raised to the power of x
• $exp2(x) - float - 2 raised to the power of x
• $log(x, y) - float - The base-y logarithm of x
• $logn(x) - float - The natural logarithm of x
• $log2(x) - float - The base-2 logarithm of x
• $log10(x) - float - The base-10 logarithm of x
• $lerp(x, y, amount) - float - Performs a linear interpolation between two values based on the given weight. Params: x — The first value, which is intended to be the lower bound. y — The second value, which is intended to be the upper bound. amount — A value between 0 and 1, that indicates the weight of the interpolation.
• $dialog(dialogKey) - string - Gets the dialog associated with the given dialog key.
• $truncate(x) - float - Truncates the value.
• $round(x) - float - Rounds the given value to the nearest even number.
• $vec(x, y) - Vector2 - Creates a Vector2 from the given coordinates.