Runaway Robot - A Mobile Runner Game

public class PlayerController : MonoBehaviour {
  // These three tuneable values affect the 'feel' of the jump.
  [Tooltip("The height of a max jump.")]
  public float maxJumpHeight;
  [Tooltip("The time to apex of a max jump.")]
  public float maxJumpTimeToApex;
  [Tooltip("The minimum amount of time before a jump can be terminated.")]
  public float minJumpTime;

  // Enable or disable double jump.
  [Tooltip("Can the player double jump?")]
  public bool canDoubleJump;

  // This mask only matches "Ground" objects, so that we can't jump off a coin.
  public LayerMask groundMask;
  // This transform is a BoxCollider parented to the player which is used to
  // check the space under the player.
  public Transform groundCheck;

  // This field tracks the amount of time the player has spent in air after
  // jumping. Should be equal to 0 if the player is grounded or if the player
  // just started their second jump.
  private float airTime = 0.0f;

  // This enum tracks the current state in the jump.
  private enum JumpPhase { Grounded, PreJump, Rising, TerminatedRising, Falling }
  private JumpPhase jumpPhase = JumpPhase.Grounded;

  // Track whether or not the player should rebound when it hits the ground.
  private bool rebound = false;
  // Check whether or not we are on the second jump of a pair.
  private bool secondJump = false;

  private Rigidbody2D rigidBody;
  void Start () { this.rigidBody = GetComponent<Rigidbody2D> (); }

  // Track whether or not gravity is inverted.
  private bool inverted = false;
  public bool Inverted {
    get { return inverted; }
    set { inverted = value; }
  }

  // Update is called once per frame
  void Update () {
    bool jump = Input.GetButtonDown ("Jump");

    // Note that the PreJump phase is used because physics must be applied in
    // `FixedUpdate`, but inputs have to be collected in `Update`.

    if (canDoubleJump && !secondJump && jumpPhase != JumpPhase.Grounded && jump) {
        airTime = 0.0f; // Reset air-time.
        rebound = false; // Reset the rebound flag.
        secondJump = true; // We are on our second jump.
        jumpPhase = JumpPhase.PreJump; // Move to the PreJump phase.
    }

    if (jumpPhase == JumpPhase.Grounded && (jump || rebound)) {
        rebound = false; // Reset the rebound flag.
        secondJump = false; // We are on our first jump.
        jumpPhase = JumpPhase.PreJump; // Move to the PreJump phase.
    }

    // Queue up a jump if the player tries to jump while we are falling.
    if (jumpPhase == JumpPhase.Falling && jump) {
      rebound = true;
    }
  }

  void FixedUpdate() {
    // Calculate gravity.
    float gravity = (-2 * maxJumpHeight) / (maxJumpTimeToApex * maxJumpTimeToApex);
    if (inverted) gravity *= -1;
    if (jumpPhase == JumpPhase.TerminatedRising) gravity *= 3;

    // Calculate initial jump velocity.
    float jumpVelocity = (2 * maxJumpHeight) / maxJumpTimeToApex;

    // Apply the difference between real gravity and desired gravity.
    rigidBody.AddForce (new Vector2(0, gravity) - Physics2D.gravity);

    // Increment airTime.
    if (jumpPhase == JumpPhase.Grounded) airTime = 0.0f;
    else airTime += Time.fixedDeltaTime;

    // In the PreJump phase, simply apply the initial velocity.
    if (jumpPhase == JumpPhase.PreJump) {
      rigidBody.velocity = new Vector2 (
        rigidBody.velocity.x, inverted ? -jumpVelocity : jumpVelocity);
      jumpPhase = JumpPhase.Rising;
    }

    // During the Rising phase, check to see if the jump has been terminated,
    // upon which switch to the TerminatedRising phase where gravity is
    // temporarily stronger.
    if (jumpPhase == JumpPhase.Rising) {
      bool letgo = !Input.GetButton ("Jump");
      if (airTime >= minJumpTime && letgo)
        jumpPhase = JumpPhase.TerminatedRising;
    }

    if (inverted ? rigidBody.velocity.y > 0 : rigidBody.velocity.y < 0)
      jumpPhase = JumpPhase.Falling;

    if (jumpPhase == JumpPhase.Falling) {
      if (groundCheck.GetComponent<Collider2D>().IsTouchingLayers(groundMask))
        jumpPhase = JumpPhase.Grounded;
    }
  }
}