Adding Double Jump Support to a 2D Platformer Character Controller in Unity

In this tutorial, we will enhance the 2D platformer player in Unity by incorporating a double jump feature.

This modification guide assumes that you already have followed the following tutorial: 2D Character Controller for Unity.

Step 1: Declare Variables

Add the following variables to the existing script to manage the double jump feature:

public int maxJumps = 2;
int jumpsRemaining;

These variables will keep track of the maximum number of jumps allowed 'maxJumps' and the remaining jumps 'jumpsRemaining'.

Step 2: Modify Jumping Logic

Adjust the jumping logic in the 'void Update()' method to implement the double jump feature:

// Jumping
if (Input.GetKeyDown(KeyCode.W))
{
    if (isGrounded || jumpsRemaining > 0)
    {
        r2d.velocity = new Vector2(r2d.velocity.x, jumpHeight);

        // Reset jumps when grounded
        if (isGrounded)
        {
            jumpsRemaining = maxJumps;
        }
        jumpsRemaining--;
    }
}

This modification allows the player to perform a jump if grounded or still has jumps remaining.

Check the final modified script below:

'CharacterController2D.cs'

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[RequireComponent(typeof(Rigidbody2D))]
[RequireComponent(typeof(CapsuleCollider2D))]

public class CharacterController2D : MonoBehaviour
{
    // Move player in 2D space
    public float maxSpeed = 3.4f;
    public float jumpHeight = 6.5f;
    public float gravityScale = 1.5f;
    public Camera mainCamera;

    public int maxJumps = 2;
    int jumpsRemaining;

    bool facingRight = true;
    float moveDirection = 0;
    bool isGrounded = false;
    Vector3 cameraPos;
    Rigidbody2D r2d;
    CapsuleCollider2D mainCollider;
    Transform t;

    // Use this for initialization
    void Start()
    {
        t = transform;
        r2d = GetComponent<Rigidbody2D>();
        mainCollider = GetComponent<CapsuleCollider2D>();
        r2d.freezeRotation = true;
        r2d.collisionDetectionMode = CollisionDetectionMode2D.Continuous;
        r2d.gravityScale = gravityScale;
        facingRight = t.localScale.x > 0;

        if (mainCamera)
        {
            cameraPos = mainCamera.transform.position;
        }
    }

    // Update is called once per frame
    void Update()
    {
        // Movement controls
        if ((Input.GetKey(KeyCode.A) || Input.GetKey(KeyCode.D)) && (isGrounded || Mathf.Abs(r2d.velocity.x) > 0.01f))
        {
            moveDirection = Input.GetKey(KeyCode.A) ? -1 : 1;
        }
        else
        {
            if (isGrounded || r2d.velocity.magnitude < 0.01f)
            {
                moveDirection = 0;
            }
        }

        // Change facing direction
        if (moveDirection != 0)
        {
            if (moveDirection > 0 && !facingRight)
            {
                facingRight = true;
                t.localScale = new Vector3(Mathf.Abs(t.localScale.x), t.localScale.y, transform.localScale.z);
            }
            if (moveDirection < 0 && facingRight)
            {
                facingRight = false;
                t.localScale = new Vector3(-Mathf.Abs(t.localScale.x), t.localScale.y, t.localScale.z);
            }
        }

        // Jumping
        if (Input.GetKeyDown(KeyCode.W))
        {
            if (isGrounded || jumpsRemaining > 0)
            {
                r2d.velocity = new Vector2(r2d.velocity.x, jumpHeight);

                // Reset jumps when grounded
                if (isGrounded)
                {
                    jumpsRemaining = maxJumps;
                }
                jumpsRemaining--;
            }
        }

        // Camera follow
        if (mainCamera)
        {
            mainCamera.transform.position = new Vector3(t.position.x, cameraPos.y, cameraPos.z);
        }
    }

    void FixedUpdate()
    {
        Bounds colliderBounds = mainCollider.bounds;
        float colliderRadius = mainCollider.size.x * 0.4f * Mathf.Abs(transform.localScale.x);
        Vector3 groundCheckPos = colliderBounds.min + new Vector3(colliderBounds.size.x * 0.5f, colliderRadius * 0.9f, 0);
        // Check if player is grounded
        Collider2D[] colliders = Physics2D.OverlapCircleAll(groundCheckPos, colliderRadius);
        //Check if any of the overlapping colliders are not player collider, if so, set isGrounded to true
        isGrounded = false;
        if (colliders.Length > 0)
        {
            for (int i = 0; i < colliders.Length; i++)
            {
                if (colliders[i] != mainCollider)
                {
                    isGrounded = true;
                    break;
                }
            }
        }

        // Apply movement velocity
        r2d.velocity = new Vector2((moveDirection) * maxSpeed, r2d.velocity.y);

        // Simple debug
        Debug.DrawLine(groundCheckPos, groundCheckPos - new Vector3(0, colliderRadius, 0), isGrounded ? Color.green : Color.red);
        Debug.DrawLine(groundCheckPos, groundCheckPos - new Vector3(colliderRadius, 0, 0), isGrounded ? Color.green : Color.red);
    }
}

Step 3: Test Your Game

Run your game in Unity and test the double jump feature. The character should be able to jump twice in mid-air after leaving the ground.