Code

extends KinematicBody

var speed = 250
var direction = Vector3()
var gravity = -9.8
var velocity = Vector3()

func _ready():
	pass

func _physics_process(delta):
	direction = Vector3(0,0,0)
	if Input.is_action_pressed("ui_left"):
		direction.x -= 1
	if Input.is_action_pressed("ui_right"):
		direction.x += 1
	if Input.is_action_pressed("ui_up"):
		direction.z -= 1
	if Input.is_action_pressed("ui_down"):
		direction.z += 1
	direction = direction.normalized()
	direction = direction * speed * delta

	if velocity.y > 0:
		gravity = -20
	else:
		gravity = -30

	velocity.y += gravity * delta
	velocity.x = direction.x
	velocity.z = direction.z

	velocity = move_and_slide(velocity, Vector3(0,1,0))

	if is_on_floor() and Input.is_key_pressed(KEY_SPACE):
		velocity.y = 5