Godot Platformer Lesson 1a: Player Movement
===============================================

Summary
--------

This lesson covers player jumps.

Prerequisites
--------------

* :doc:`Lesson 1a: Player Movement<1a-player-movement>`

Video
--------

.. raw:: html

   <iframe width="560" height="315" src="https://www.youtube.com/embed/Mc13Z2gboEk?start=2875&end=4242" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>


Resources
-----------

Assets: https://github.com/GDQuest/godot-beginner-2d-platformer/releases/tag/1.1.0

Errata
-----------

link: https://www.gdquest.com/tutorial/godot/2d/your-first-game/chapter/1-player-and-enemy/

For this video there is a value updated at 1:02:26 that is not mentioned in the video.


Notes
-----------

* In MacOS replace is accessed using command-f


Code
--------

Repository: https://github.com/los-alamos-steam-lab/GDQuest-Platformer/tree/1b-player-jump

Actor Code
^^^^^^^^^^^^^^^^^^^^

.. code-block:: gdscript

    extends KinematicBody2D
    class_name Actor

    const FLOOR_NORMAL = Vector2.UP

    export var speed := Vector2(300, 1000)
    export var gravity := 4000.0

    var _velocity := Vector2.ZERO
        
    

Player Code
^^^^^^^^^^^^^^^^^^^^

.. code-block:: gdscript

    extends Actor

    func _physics_process(delta):
        var is_jump_interrupted: = Input.is_action_just_released("jump") and _velocity.y < 0
        var direction := get_direction()
        _velocity = calculate_move_velocity(_velocity, direction, speed, is_jump_interrupted)
        _velocity = move_and_slide(_velocity, FLOOR_NORMAL)

    func get_direction() -> Vector2:
        return Vector2(
            Input.get_action_strength("move_right") - Input.get_action_strength("move_left"), 
            -1.0 if Input.is_action_just_pressed("jump") and is_on_floor() else 0.0
        )
        
    func calculate_move_velocity(linear_velocity: Vector2, direction: Vector2, speed: Vector2, is_jump_interrupted: bool) -> Vector2:
        var new_velocity: = linear_velocity
        new_velocity.x = speed.x * direction.x
        new_velocity.y += gravity * get_physics_process_delta_time()
        if direction.y == -1:
            new_velocity.y = speed.y * direction.y
        if is_jump_interrupted:
            new_velocity.y = 0
        return new_velocity

Common Problems
------------------

* Player not jumping when on floor:
    * Sometimes :code:`is_on_floor()` can be a bit buggy.  If you supply a second argument \
      to :code:`move_and_slide()` then it will know which direction the floor (or rather the \
      ceiling) is.  So we want :code:`velocity = move_and_slide(velocity, Vector2.UP)`. This \
      is covered in the video if you are patient, but it can seem like you made a mistake if \
      you're testing your code as you go.