Jump with Space

This example jumps from one flat floor, falls under gravity, and allows another jump after landing. It works with a rigid body or a jelly body. For slopes, moving platforms and coyote time, use Platformer Controller and its own Jump binding.

Set up input and physics

1. Open Settings → Project Input → Gameplay → Jump · Space. If Jump already exists, check that it is a Button action with a Space binding.
2. Give the player Rigid Body 2D (Dynamic, Gravity Scale 1, Lock Rotation on) and Collider 2D. For a jelly, use Soft Body 2D with Gravity Scale 1 and no pinned particles instead; do not add a rigid body to it.
3. Create a wide floor below the player. Add Collider 2D, with Sensor off. A collider without a rigid body acts as a fixed floor. Start the player slightly above it.
4. In Scripts → New Behavior, replace the starter class with the complete source below and Save & Apply.
5. In Arrange, add Jump to the player. Set its Ground property to the floor object. Leave Jump Speed at 420 to start.
6. Press Play, click the game to focus it, let the player land, and press Space. Release and press again after landing to jump again.

Complete script

class Jump : Component {
    [Property] float JumpSpeed = 420;
    [Property] Entity Ground;
    bool grounded;

    void Update(float dt) {
        if (!grounded || !Input.Pressed("Jump")) return;
        RigidBody2D body = GetComponent<RigidBody2D>();
        SoftBody2D jelly = GetComponent<SoftBody2D>();
        if (body != null) body.SetVelocity(new Vector2(body.Velocity.X, -JumpSpeed));
        else if (jelly != null) jelly.SetVelocity(new Vector2(0, -JumpSpeed));
        grounded = false;
    }

    void OnCollisionStart(Entity other) {
        if (Ground != null && other == Ground && Transform.WorldPosition.Y < Ground.WorldPosition.Y) grounded = true;
    }

    void OnCollisionEnd(Entity other) {
        if (other == Ground) grounded = false;
    }
}

Input.Pressed("Jump") reads the action named Jump, not a physical key. It is true once per press. SetVelocity uses pixels per second: negative Y moves up. Unlike an impulse, the same velocity produces the same initial speed regardless of mass. The rigid-body branch preserves horizontal velocity; the soft-body branch sets it to zero.

The contact hooks enable jumping on the selected floor and disable it when leaving. This is a single-floor example, not general ground detection. ContactCount includes walls and ceilings and should not be treated as “standing on the ground.”

Find the broken step

What happens	Check
Input's Jump meter does not react during Play	Focus the game, release Space, and press again. Verify Jump is a Button with a Space binding in Gameplay.
The meter reacts but the player stays still	Jump is attached and enabled; Ground points to the floor; both colliders are non-sensors; the rigid body is Dynamic or the soft body has movable particles.
The body moves only a tiny amount with an impulse	Impulse depends on mass. This recipe uses SetVelocity for a predictable starting speed.
The body falls through the floor	The floor needs Collider 2D, Sensor off. A rigid-body player also needs Collider 2D.
It works until another script is enabled	Another controller or script may replace velocity or position each frame. Choose one movement owner.

API reference

• Input: Pressed, Held, Released, Axis and Vector
• RigidBody2D: velocity, impulse and body modes
• SoftBody2D: velocity, impulse and live solver values
• Component: lifecycle and collision hooks