Docs · Make it move

Characters and physics

Make the room solid

1. If crate 1 still carries the Mover from Getting started, remove it with the bin icon at the right of its header. Otherwise the crate slides away through the wall.
2. Delete crate 2 and crate 3: select each in the Hierarchy and press Delete. The floor between crate 1 and the right wall is where this guide puts some steps, a ledge, a plate and a door.
3. Select floor. In the Inspector, press Add component, type collider and choose ColliderComponent.
4. Set the Collider’s Size to the Shape’s: 640 and 24. Both are centred on the node, so now they cover the same box.
5. Do the same for ceiling, wall left, wall right and crate 1, each Collider the size of its own Shape. Leave backdrop alone: it is the wall behind the room, and nothing stands on it.

Kind

Rectangle, Circle or Capsule. A rectangle blocks as its box. A solid circle or capsule blocks along its curve: it is cut into boxes, each as long as the Collider’s Step, so a character stands on the round of it and not on the corner of a square. A shorter Step follows the curve more closely and costs more boxes. At 0 nothing is cut and a round Collider blocks as its box again. Step is in the Polygon fold and starts at 32.

Size

The box, in world units, centred on the node. It does not scale with the node.

Outline and Step

Points that replace the box, for a shape a box cannot make. A slanted edge in the outline becomes a staircase of boxes, each Step long. The next sections say how a character climbs one.

Offset

Moves the box off the node’s centre.

Solid

Whether it blocks at all. Untick it and it stops nothing, and it notices nothing either: a character passes through and no script hears it. If you come from Unity, Solid off is not isTrigger, which notices: what notices here is an Area, below, as in Godot.

One Way

Blocks a character only as it comes down onto it. See below.

Layer, Include Layers and Exclude Layers

Layer is what the Collider is on: a row of boxes behind a button, one for each collision layer the project names. Which layers meet is the Collision matrix on the Physics tab of File → Project settings…: a pair ticked meets, a pair unticked passes through each other, and every pair comes ticked, so a project that never opens it has every character meet every Collider. Include Layers and Exclude Layers override the matrix for this one Collider, whichever of the two Colliders in a contact carries them. A body on an included layer meets it whatever the matrix says, a body on an excluded layer passes through it, and Exclude wins. Neither changes what the Collider is on. Tiles answer to the matrix alone, so neither reaches them. A Collider with no layer ticked is on none, and the matrix lets nothing meet it, so leave all three as they start. Crates puts a project’s layers to work.

Material

Tick it for Friction and Bounce. Bounce throws a character that lands on it back up: at 1 it rises nearly as high as it fell from, and at 0 it stops dead. Friction is felt. Under 1, the keys bring a character up to its walking speed, and back down to a stop, a little each step, so a low Friction is ice: at 0.1 it takes a second to reach its walk and a second to stop. 1 or more is plain ground, where the keys have it at once. Ice and bounce lays a strip of ice.

A character that walks

1. Select Room and press + Add node → Character. The new node carries a Character Body, and a Shape to see it by. Name it player.
2. Set its Position to -250 and 156: the left of the room, with its feet on the floor.
3. Make the Shape match the body. Set its Kind to Capsule, its Size to 32 and 48, its Anchor to 0.5 and 1, and its Sort Layer to 10, so the character draws in front of crate 1.
4. Press F5. Walk with A and D, or Left and Right, and jump with Space or W. The character stops at the walls and at crate 1, and jumps up onto it.

Size

The box it collides as, in world units, standing on the node.

Motion Mode

Grounded falls, stands on floors and jumps. Floating has no down: no gravity, no jumping, and one-way platforms do not stop it. The keys walk a floating body four ways: left and right across, up and down up and down, which are A, D, W and S, or the arrows, until you bind others.

Velocity

How fast it is moving, in units per second, with down positive. The keys set its left-right part every step.

Drift

What the world adds to its own Velocity, in units per second: a wind, a belt, a magnet, water, a shove, a swing. The body moves by the two together. You cannot type it: the world writes it, so the row is dim. The keys set Velocity every step and never touch Drift, so a gust is not undone a step later. A Godot CharacterBody2D or a Unity Rigidbody2D has one velocity, which the next line that sets it wipes; this body keeps the two apart. The updraft shows it live.

Gravity

How quickly it speeds up as it falls.

Terminal Velocity

The fastest it falls.

Speed

How fast it walks, in units per second.

Driven By

Who walks it and makes it jump. Keys, the default, walks it on your controls, as above, and every body in this guide is one. A Grounded body the keys walk also turns to face its walk: walking left mirrors the Flip X of the Sprite on its node, walking right puts it back, and standing, or holding both keys, keeps the way it last faced. So draw its art facing right. A Floating body is not turned, and neither is one driven by a script. Script leaves both to the body’s own script: it writes the body’s sideways speed with set_number("CharacterBodyComponent", "velocity.x", …) and asks for a jump with jump, and the keys leave it alone. Gravity, floors, walls and ledges work the same either way. The knight, the patrolling enemies and the boss of Crypt Knight are bodies driven by a script.

Jump Speed

The upward speed a jump starts with. At the defaults, 620 against a Gravity of 1800, a jump rises about 100 units.

Coyote Time

Seconds after it runs off a ledge in which a jump still counts, as if from the ground. At the default, 0, there is no grace. About a tenth of a second forgives a jump that comes a hair late.

Jump Buffer

Seconds a jump asked for just before landing waits to happen on landing. At 0, a jump asked for in the air is lost; about a tenth of a second makes a press that comes a moment early still a jump.

Jump Cut

How much of the upward speed is kept when the jump is let go early, from 0 to 1. At the default, 1, all of it: a tap rises as far as a held jump. At 0.5 a tap rises about a quarter as high. A body driven by the keys is cut by letting go of the jump key; one driven by a script calls cut_jump.

Air Jumps

How many more jumps it may make in the air before it lands again, each a fresh press. At the default, 0, a body jumps only from the ground. A script may write it: Crypt Knight’s double jump is a relic that sets it to 1.

Swim Stroke

In the Jumping fold: the upward speed a press of jump gives it in water, in units per second. While the middle of its box is under the waterline of a Buoyancy effector, and it is neither on the ground nor within its Coyote Time, a press sets its upward speed to this, once for each press. At the default, 0, it cannot swim. The flooded cellar floats a knight and gives him a stroke.

Rope Jump

In the Jumping fold: the upward speed a press of jump gives it while it hangs on a rope, in units per second: held by an enabled Joint, off the ground and outside its Coyote Time. It does not let go of the rope: the script that holds the Joint does. At the default, 0, a press on a rope does nothing. The grapple swings a knight on one.

Pushable

In the Pushing fold. Ticked, a body that walks into this one shoves it along instead of stopping at it: a crate. It needs a solid Collider of its own to be walked into. Crates builds three.

Push Speed

In the Pushing fold: how much of the pusher’s walk a shove gives this body, from 0 to 1. At 1 it keeps pace with the pusher; at 0.5, the default, it moves at half its speed, and the pusher with it.

Grounded, On Wall and On Ceiling

What the last step found: something solid underfoot, something in the way to the side, something overhead. The engine sets them, and you can watch them change in the Inspector while the room plays.

Shoving

Ticked on a step this body shoved a Pushable body along. It is not ticked when it walks free, nor when what it walks into will not give way: then it is On Wall instead. The engine sets it, as it sets On Wall. Crates reads it live.

Drop Through

On while it drops through a one-way platform, which then holds it up no more, and off again by itself once its feet are below the platform’s top. That is the same step it leaves the platform, so you will seldom see it ticked. The keys turn it on for a body they drive when down, S or Down, is held as jump, Space, is pressed on a one-way platform, and a script’s drop_down() turns it on for any body. See below.

Layer

Which collision layers the body is on, a row of boxes behind a button, ticked by name like a Collider’s Layer. It meets the Colliders and the tiles its layers meet in the Collision matrix, except where a Collider’s Include Layers or Exclude Layers say otherwise. A new body is on the first layer, as a new Collider is, and every pair of layers meets until you untick one, so a project that never touches layers sees no difference.

Debug Color

The colour Debug draw fills its box with.

Steps and slopes

1. Select Room, add a node with + Add node → Shape, name it step 1, and give it a Collider as in the first section.
2. Press Ctrl+D twice, and name the copies step 2 and step 3.
3. Set all three from the table below, typing each size into both the Shape’s Size and the Collider’s.
4. Press F5, jump crate 1, and walk right into the steps. Each one stops the character like a wall, and it has to jump them.

1. Select player. In its Character Body’s Slopes fold, set Step Height and Floor Snap Length to 18, a little over the 16 each step rises.
2. Press F5 and walk right. The character walks up the steps without jumping. Walk back left, and it walks down them without leaving the ground.

Step Height

The tallest step it walks up without jumping. At 0, the default, it stops at every one.

Floor Snap Length

How far down it reaches to stay on the ground as it walks downhill. At 0 it leaves the ground at the edge of every step on the way down, and lands again on the next.

Floor Max Angle

In radians. A staircase steeper than this is a wall. The default, 0.7854, is 45°. The steepness is measured from how far the character has walked since it last stepped up, so a character that starts right against a step, with no room to walk into it, does not climb it.

Max Slides

How many times in one step a move that ran into something tries again with what is left of it. Raise it to 2 or 3 if the character catches on corners that look smooth.

A ledge you jump up through

1. Select Room, add a node with + Add node → Collider, name it ledge, and set its Position to 80 and 44: high over the right half of the room, just past the top step.
2. Set its Collider’s Size to 160 and 8, and tick One Way.
3. A Collider draws nothing in the game. Press Add component, choose ShapeComponent and give the Shape the same Size, so there is a ledge to see.
4. Press F5, walk up the steps and jump from the top one. The character rises through the ledge and lands on top. From the floor it is out of reach.

1. Press F5, get onto the ledge, hold S and press Space. The character drops through to the floor, and the ledge holds it again the next time it jumps up onto it.

1. In Assets, choose Create → New script, type drop_down and press Create.
2. In the Code panel, click drop_down.rgs in its Scripts list, replace its text with the script below, and press Ctrl+S.
3. Select player, press Add component, type drop and choose DropDown.
4. Press F5, get onto the ledge, and press S or Down. The character drops through to the floor, and the ledge holds it again the next time it jumps up onto it.

/// Press down to drop through the one-way platform underneath.
component DropDown : Body {
    fn loop() {
        if pressed("down") {
            drop_down();
        }
    }
}

component DropDown : Body

The : Body says the script belongs on a node with a Character Body, and gives it the hooks a body has, which come further down. See Body.

fn loop()

Runs every step. A hook may leave out a parameter it does not use: this one’s is dt.

pressed("down")

True on the one step the player presses down: S or Down. See pressed.

drop_down()

Asks the Character Body on the same node to drop through the one-way ledge it stands on. On solid ground, or in the air, it does nothing. See drop_down.

Reading the controls

held(action)

True on every step the action is held down. See held.

pressed(action)

True only on the step it goes down. A tap is one pressed, however long the key stays down. See pressed.

direction(action)

A two-way action, made of four keys or a stick, as a Vec2: right minus left across, down minus up. The default controls have no two-way action, so it answers zero until your project’s controls define one. See direction.

/// Runs while the action key is held.
component Sprint : Body {
    walk: f32 = 220.0,
    run: f32 = 400.0,

    fn loop() {
        if held("action") {
            set_number("CharacterBodyComponent", "speed", run);
        } else {
            set_number("CharacterBodyComponent", "speed", walk);
        }
    }
}

When a character lands

on_land()

It touches the ground after being in the air. See on_land.

on_leave_ground()

It leaves the ground: a jump, or a walk off an edge. See on_leave_ground.

on_hit_wall()

Something stops it moving sideways. See on_hit_wall.

on_hit_ceiling()

Something stops it moving up. See on_hit_ceiling.

/// Squashes the character for a moment each time it lands.
component Squash : Body {
    fn on_land() {
        await anneal_scale(vec2(1.3, 0.7), 0.05, .OutQuad);
        anneal_scale(vec2(1.0, 1.0), 0.15, .OutBack);
    }
}

Areas that notice

1. Select player, press Add component and choose AreaComponent. In its Shape, set Size to 32 and 48 and Offset to 0 and -24. An Area is centred on its node, and the Offset lifts this one over the body, which stands on the node.
2. Select Room, add a node with + Add node → Area and name it plate. Set its Position to 100 and 152, on the floor under the ledge, and its Shape’s Size to 64 and 12.
3. An Area draws nothing in the game either. Give plate a Shape too, 64 by 8, so there is a plate to see.

Shape

The volume, centred on the node. Only its Kind, Size, Outline and Offset count. Its other rows are a Collider’s, and an Area never blocks anything.

Layer

Which layers this Area is on.

Mask

Which layers it looks for. An Area notices another when its Mask shares a layer with the other’s Layer. Every Area starts on the first layer and looking for it, so every Area notices every other until you change them.

Track

Leave it empty. A Track switches the Area on only while an Animated Sprite on its node shows a frame that track marks, in the editor and in an exported game: an attack’s hitbox, live for the frames of the swing.

/// Tells the nodes it is wired to when something steps on it.
component Plate : Area {
    fn on_enter() {
        emit("pressed");
    }
}

Wire the plate to a door

1. Select Room, add a node with + Add node → Shape and name it door. Set its Position to 200 and 108, and its Shape’s Size to 24 and 96: a tall bar standing on the floor, between the plate and the right wall.
2. Give it a Collider of the same size, as in the first section. Press F5: the door stops the character.
3. Select plate, press Add component and choose SignalComponent. Press + beside Connections, and open the new [0] row.
4. Type pressed into Signal, spelled exactly as the script emits it. Click To and choose door.

1. Make a script called door the way you made drop_down.rgs, and replace its text with the one below.
2. Select door, press Add component, type door and choose Door.
3. Press F5 and walk onto the plate. The door disappears, and the character walks on through where it stood.

/// Opens when a plate wired to it is pressed.
component Door {
    fn on_signal() {
        if heard("pressed") {
            hide();
        }
    }
}

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