Introduction
In this tutorial, we will be continuing our code from the previous tutorial by adding a jumping mechanic for our player.
Jumping
We will utilize Button A for jumping. In order to jump, we need to give a relatively large value to player.speed_y e.g -190. The value is negative since we need the player to move upwards. We will also assign a global variable player_jumpSpeed
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player_jumpSpeed = -190
if rpy.btnADown():
player.speed_y = player_jumpSpeed
Our player can now jump. However, if you continuously press the A Button, the player will be able to jump out of the screen. This is undesirable and we would like to jump once.
To avoid this, we will have to keep track of the player’s position and allow him to jump only if he is on the ground by using the code below:
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if player.bot_y > groundLevel:
player.bot_y = groundLevel-1
Let’s create another global variable player_isGrounded = False and set it to True when he has hit the ground.
Once everything is implemented, the code should look as follows:
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player_walkSpeed = 50
player_jumpSpeed = -190
player_isGrounded = False
gAcc = 300
groundLevel = 238
def update(dt):
global player_isGrounded, player_walkSpeed, player_jumpSpeed, gAcc, groundLevel
if rpy.btnLeftDown():
player.currNdx(0, 1)
player.speed_x = -player_walkSpeed
if rpy.btnRightDown():
player.currNdx(0, 0)
player.speed_x = player_walkSpeed
if rpy.btnLeftUp():
player.speed_x = 0
if rpy.btnRightUp():
player.speed_x = 0
if rpy.btnADown() and player_isGrounded:
player.speed_y = player_jumpSpeed
player_isGrounded = False
player.acc_y = gAcc
player.update(dt)
if player.bot_y > groundLevel:
player.bot_y = groundLevel-1
player_isGrounded = True
Double Jump / Multiple Jumps
To achieve multiple jumps, we need to keep track of a few more states.
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player_isJumping = False
player_jumpCount = 0
player_jumpMax = 2
We need to check if player is Jumping with player_isJumping We need to track how many multiple jump has been made and make sure that it doesn’t exceed the maximum player_jumpMax.
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if player_isGrounded:
player.acc_y = 0
player.speed_y = 0
player_jumpCount = 0
player_isJumping = False
if rpy.btnADown():
player.speed_y = player_jumpSpeed
player_jumpCount += 1
player_isGrounded = False
player_isJumping = True
else: # in the air
player.acc_y = gAcc
if rpy.btnADown():
if player_jumpCount < player_jumpMax and player_isJumping:
player.speed_y = player_jumpSpeed
player_jumpCount += 1
Again, don’t forget to add the globals: global player_isJumping, player_jumpCount, player_jumpMax
At this point you will be able to do a double jump to increase the number of multiple jumps, just change the value of player_jumpMax
Full code:
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from retroPy import rpy, actor, LoadSprite
p_player = LoadSprite("playerT.rs4")
player = actor(p_player, 112, 112, 0, 0, 0)
player.currNdx(0)
player_walkSpeed = 50
player_jumpSpeed = -190
player_isGrounded = False
player_isJumping = False
player_jumpCount = 0
player_jumpMax = 2
gAcc = 300
groundLevel = 238
def update(dt):
global player_isGrounded, player_walkSpeed, player_jumpSpeed, gAcc, groundLevel
global player_isJumping, player_jumpCount, player_jumpMax
if rpy.btnLeftDown():
player.currNdx(0, 1)
player.speed_x = -player_walkSpeed
if rpy.btnRightDown():
player.currNdx(0, 0)
player.speed_x = player_walkSpeed
if rpy.btnLeftUp():
player.speed_x = 0
if rpy.btnRightUp():
player.speed_x = 0
if player_isGrounded:
player.acc_y = 0
player.speed_y = 0
player_jumpCount = 0
player_isJumping = False
if rpy.btnADown():
player.speed_y = player_jumpSpeed
player_jumpCount += 1
player_isGrounded = False
player_isJumping = True
else: # in the air
player.acc_y = gAcc
if rpy.btnADown():
if player_jumpCount < player_jumpMax and player_isJumping:
player.speed_y = player_jumpSpeed
player_jumpCount += 1
player.update(dt)
if player.bot_y > groundLevel:
player.bot_y = groundLevel-1
player_isGrounded = True
def draw():
global player_walkSpeed, gAcc, groundLevel
rpy.clear()
player.draw()
rpy.hline(0, groundLevel, 240, 7)
#=========================================================================
rpy.run(update, draw)