Wall-Jumping

Wall-Jumping is a technique used in Scratch to make sprites bounce off walls. This allows a character in a project, for instance, to scale up massive heights of walls rather than jumping on individualized sections like stairs. It is commonly used in platformers.

Method

This is just one of the ways for wall jumping to work.

Three variables are needed for this method to operate properly:

• L-vel — The velocity of the player going left
• R-vel — The velocity of the player going right
• Y-vel — The velocity of the player on the y axis

Afterwards, a player sprite should be made. This is the sprite that will perform all motions and be physically wall-jumping. An example of a player sprite is shown below:

The colours on each side of the square are the sensors that will use to "sense" which side the wall and floor are relative to the character. Using more complicated coding, it wouldn't require colours.

Two separate scripts are needed then, one for moving and one for sensing walls:

when gf clicked
set [R-vel v] to [0]
set [L-vel v] to [0]
forever
if <key (right arrow v) pressed?> then
change [R-vel v] by (1)
end
if <key (left arrow v) pressed?> then
change [L-vel v] by (1)
end
if <key (up arrow v) pressed?> then
if <color [#0000FF] is touching [#000000]?> then
set [Y-vel v] to [20]
broadcast (Jump v)
end
end
if <not <color [#0000FF] is touching [#000000]?>> then
change y by (-5)
end
if <color [#FF0000] is touching [#000000]?> then
set [Y-vel v] to [0]
set [R-vel v] to [0]
if <not < <color [#0000FF] is touching [#000000]?> or <key (up arrow v) pressed?> > > then
wait (0.5) secs
if <key (up arrow v) pressed?> then
set [Y-vel v] to [20]
broadcast (Jump v)
end
set [L-vel v] to [10]
end
end
if <color [#00FF00] is touching [#000000]?> then
set [Y-vel v] to [0]
set [L-vel v] to [0]
if <not < <color [#0000FF] is touching [#000000]?> or <key (up arrow v) pressed?> > > then
wait (0.5) secs
if <key (up arrow v) pressed?> then
set [Y-vel v] to [20]
broadcast (Jump v)
end
set [R-vel v] to [10]
end
end
change x by (R-vel)
change x by ((0) - (L-vel))
change [R-vel v] by ((R-vel) * (-0.2))
change [L-vel v] by ((L-vel) * (-0.2))

And one for jumping:

when I receive [Jump v]
repeat (10)
if <color [#FFFF00] is touching [#000000]?> then
set [Y-vel v] to [0]
stop [this script v]
end
change y by (Y-vel)
change [Y-vel v] by (-1)
end
set [Y-vel v] to [0]

There is another way of doing it. One variable is needed

• velocity — The velocity of the player's horizontal movement.

when gf clicked
forever
if <key (left arrow v) pressed?> then
change [velocity v] by (-1)
end
if <key (right arrow v) pressed?> then
change [velocity v] by (1)
end
if <not <touching (ground v)?>> then
change y by (-10)
end
if <key (up arrow v) pressed?> then
change y by (60)
end
change y by (1)
change x by (velocity)
if <touching (ground v)?> then
change x by ((0)-(velocity))
if <key (up arrow v) pressed?> then
change y by (60)
change x by ((0)-(velocity))
end
change y by (-1)
set [velocity v] to ((velocity)*(0.75))
end

Method 2

An easier way uses very simple coding. The sprite can be any color, and no velocity script is needed. Gray should be the color of the walls.

when gf clicked
set [wall jump v] to (0)
forever
if <<<not<touching color [#000000]?>>and<touching color[#444444]?>>and<<key (space v) pressed?>or<key (up arrow v) pressed?>>> then
if <not<(wall jump)=(1)>> then
set [wall jump v] to (1)
repeat (10)
change y by (15)
end
wait until <color [#0000FF] is touching [#000000]?>
set [wall jump v] to (0)
end

A separate code is needed to make movement.

when gf clicked
forever
if <key (left arrow v) pressed?> then
change x by (-4)
end
if <key (right arrow v) pressed?> then
change x by (4)
end
if <<key (space v) pressed?>and<color [#0000FF] is touching [#000000]?>> then
repeat (10)
change y by (15)
end
end
if <not<color[#0000FF] is touching [#000000]?>> then
change y by (-7)
end
if <color [#FFFF00] is touching [#000000]?> then
change y by (-8)

Examples

• Wall jump engine (the script that was used for this article)

See Also

• Platformer