View source for Scrolling Platformer Tutorial

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{{about|how to make a scrolling platformer|a basic platformer tutorial|How to Make a Basic Platformer|advanced platformer physics|Advanced Platformer Physics}}
This article covers a step-by-step process about how to make a '''[[Scrolling Platformer]]'''. A scrolling platformer is a type of platformer where the camera follows the player as they move through the level(s).

==Coding the Player Sprite==
To code the movement of the player, the following scripts need to be made. All scripts in this section are to go in the 'Player' sprite.

{{note|Variables in capital form (e.g. "SCROLL X" and "SCROLL Y") are global variables, and those lowercase (e.g. "x" and "y") are made with the "For this sprite only" option selected.}}

<scratchblocks>
When green flag clicked
broadcast (Green Flag v) and wait//A way to only need 1 flag block. Flag blocks create lag, so the fewer the better.{{cn}}
broadcast (Play Game v) and wait//Broadcasts to the other sprites that the game has started.

When I receive [Play game v]
forever
broadcast (Reset v) and wait
    broadcast (Set Up v) and wait
    Game On::custom//Sets up the variables.
    repeat until <(EXIT)>()>//This means the player has either died or won.
        broadcast (Tick v)
    end
    if <(EXIT)=(win)> then
        Win::custom
    else
        Die::custom//If the player did not win, they would have died.
    end

define Position
go to x:((x)-(SCROLL X)) y: ((y) - (SCROLL Y)

define Game On//Run without screen refresh.
point in direction (90)
set size to (100)%
clear graphic effects
set [in air v] to (0)
set rotation style [left-right v]
set [sy v] to (0)
set [x v] to (0)
set [y v] to (0)
set [EXIT v] to () //This should be blank.
set [SCROLLL X v] to (0)
set [SCROLLL Y v] to (0)
show

When I receive [Tick v]
broadcast (Ready v)
Tick <key (Right arrow v) pressed?> <key (Up arrow v) pressed?> <key (Left arrow v) pressed?>::custom//Checks if a key has been pressed.

define Tick <right> <up> <left>
if <left> then//If the left key was pressed, it moves the player left.
    Change player X by [-8]::custom
end
if <right> then//If the right key was pressed, it moves the player right.
    Change player X by [8]::custom
end
if <<up> and <(in air)< (4)>> then//If the up key was pressed, it checks if they are still in the air. If they are not, it makes the player jump.
    set [sy v] to (16)
end
change [sy v] by (-1)//Set sy to any negative number.
Change player Y by (sy)::custom//Actually moves the player's Y position.
Test dying::custom//Checks if the player has hit a danger sprite.
if <(SCROLL X)<(0)> then
    set [SCROLL X v] to (0)
end
if <(SCROLL Y)<(0)> then
    set [SCROLL Y v] to (0)
end
change [SCROLL Y v] by (round(((y)-(SCROLL Y))/(10)))
change [SCROLL X v] by (round(((x)-(SCROLL X))/(5)))
Position::custom//Positions the player's location correctly.
if <(y position) < (-180)> then//Checks if the player has fallen into the abyss.
    set [EXIT v] to [die]
end

define Change player X by (sx)//Moves the player's X axis.
if <(sx::custom)<(0)> then//If the player is moving left.
    point in direction (-90)//They point left.
else
    point in direction (90)//They point right.
end
change [x v] by (sx::custom)//Changes the X variable by the amount of movement needed (sx).
Position::custom//Positions the player.
if <touching (platforms v) ?> then//Will check if the player has hit a wall or a slope.
    repeat (12)//Will check if the wall/slope is 12 pixels steep or not.
        change [y v] by (1)//Moves the player up 1 pixel.
        Position::custom//Positions the player.
        if <not<touching (platforms v) ?>> then//That means it was a slope, so the player can stop trying.
            stop [this script v]
        end
    end
    change [y v] by (-12)//Corrects for the 12 that was used above.
    repeat until <not<touching (platforms v)?>> //Repeatedly checks is the player has ran into a wall.
        if <(sx)>(0)> then //To see if the player is moving left of right.
            change [x v] by (-1) //The player is trying to move right, so we need to move left to not go into the wall.
        else
            change [x v] by (1) //The player is trying to move left, so we need to move right to stay out of the wall.
        end
        Position::custom //Reposistions the player on the scrolling plane.
    end
end

define Change player Y by (sy)
change [y v] by (sy::custom) //Changes the y variable by (sy).
change [in air v] by (1) //This is so that we know if we are in the air or on the ground. Without this, the player would be able to hold jump and just fly.
Position::custom //Reposistions the player.
repeat until <not<touching (platforms v)?>>
    if <(sy::custom)>(0)> then
        change [y v] by (-1)
    else
        change [y v] by (1)
        set [in air v] to (0)
    end
    set [sy v] to (0)
    Position::custom
end

define Test dying
if <touching (Danger v)?> then
    set [EXIT v] to [die]
end

define Die
set [EXIT v] to ()//This is empty.
repeat (4)
    hide
    wait (0.1) seconds
    show
end
wait (0.5) seconds

define Win
set rotation style [don't rotate v]
repeat (50)
    point towards (Portal v)
    turn cw (65) degrees
    move ((distance to (Portal v))/(2)) steps
    change size by (-1)
    change [ghost v] effect by (2)
end
hide
change [LEVEL v] by (1)
wait (1) seconds
clear graphic effects
set rotation style [left-right v]
</scratchblocks>

==Coding the Platforms Sprite==
Once the player's code has been completed, the ground sprite (called 'platforms' here) needs to be added in order to create a scrolling effect. The following scripts go in the 'platforms' sprite.

<scratchblocks>
when I receive [Tick v]
Position ((x)-(SCROLL X)) ((y) - (SCROLL Y)
when I receive [Green flag v]
show

define Position (x) (y)
go to x: (x::custom) y: (y::custom)
if <<(x::custom)= (x position)> and <(y::custom) = (y position)>> then
    show
else
    hide
end

When I receive [Setup v]
set [x v] to (0)
set [y v] to (0)
if <(LEVEL)=(1)> then
    switch costume to (Level 1 1)
    Clone (450) (0) // This clones a new level. This needs to be done as many times as the number of levels. In this case, 3 is used as an example.
    Clone (450) (0)
    Clone (450) (0)
else
    ...::grey // If there is another scene, it should be cloned here using another if else block.
end

define Clone (x) (y)
create clone of (myself v)
change [x v] by (x::custom)
change [y v] by (y::custom)
next costume
</scratchblocks>

==Coding the Danger Sprite==
To code the danger sprite, simply duplicate the "platforms" sprite and replace all the levels only with the dangerous elements that would hurt the player. {{note|Make sure to call the danger sprite "danger" because the script above already makes the player sense for a sprite of that name.}}

<scratchblocks>
when I receive [Tick v]
position ((x)-(SCROLL X))((y)-(SCROLL Y))::custom

when I receive [Green flag v]
show

when I receive [Reset v]
delete this clone

define Position (x) (y)
go to x: (x::custom) y: (y::custom)
if <<(x::custom)= (x position)> and <(y::custom) = (y position)>> then
    show
else
    hide
end

when I receive [Setup v]
set [x v] to (0)
set [y v] to (0)
if <(LEVEL)=(1)> then
    switch costume to (Level 1 1)
    Clone (450) (0) // This clones a new level. Do this as many times as the number of levels, in this case 3 is used as an example.
    Clone (450) (0)
    Clone (450) (0)
else
    ...::grey // If there is another scene, then it should be cloned here using another if else block.
end

define Clone (x) (y)
create clone of (myself v)
change [x v] by (x::custom)
change [y v] by (y::custom)
next costume
</scratchblocks>

==Coding the Portal==
Now that everything is made, a way to go to the next level needs to be made.
<scratchblocks>
When I receive [Tick v]
Position ((x)-(SCROLL X)) ((y) - (SCROLL Y))::custom
if <<(costume [number v]) = (2)> and <touching (player v)?>> then
    set [EXIT v] to [win]
end

When I receive [Setup v]
set [x v] to (0)
set [y v] to (0)
if <(LEVEL)=(1)> then
    switch costume to (Level 1 1)
    Position Portal at (450) (180)::custom
else
    ...::grey // If there is another scene, then the portal needs to be positioned here using another if else block.
end

define Position Portal at (x) (y)
set [x v] to (x::custom)
set [y v] to (y::custom)

define Position (x) (y)
go to x: (x::custom) y: (y::custom)
if <<(x::custom)= (x position)> and <(y::custom) = (y position)>> then
    show
else
    hide
end
</scratchblocks>

==Adding Collectibles==
Collectibles can be added to the game to make it more interesting. They are objects that need to be collected in order to achieve a certain goal. The code to make them is shown below:
<scratchblocks>
When I receive [Tick v]
Position ((x)-(SCROLL X)) (((y) - (SCROLL Y)) + ((([sin v] of (timer)) *(300))*(5)))::custom
if <touching (player v)?> then
    change [COLLECTED v] by (1)
    if <(COLLECTED)=(COLLECTED MAX)> then
        broadcast (Open portal v)
        start sound (All coins collected v)
    else
        start sound (Collect v)
    end
    delete this clone
end

When I receive [Green flag v]
show

when [m v] key pressed
set [MOUSE v] to (join ((mouse x) + (SCROLL X))(join [,]((mouse y) + (SCROLL Y))))

When I receive [Reset v]
delete this clone

define Position (x) (y)
go to x: (x::custom) y: (y::custom)
if <<(x::custom)= (x position)> and <(y::custom) = (y position)>> then
    show
else
    hide
end

When I receive [Setup v]
set [x v] to (0)
set [y v] to (0)
if <(LEVEL)=(1)> then
    Clone (450) (180)::custom
else
    ...::grey // If there is another scene than coins need to be cloned here using another if else block.
end

define Clone (x) (y)
set [x v] to (x::custom)
set [y v] to (y::custom)
create clone of (myself v)
change [COLLECTED MAX v] by (1)
</scratchblocks>

==Transforming a Basic Platformer==
Often, Scratchers make basic platformers before they make a scrolling platformer, and they may want to use their old script to make a scrolling platformer. To do this, the "ground" sprite would move with the player. Making a script to do this is simple:
<scratchblocks>
when green flag clicked//This goes in the player sprite.
forever
Scroll (((0) - (x position)) * (0.8)) (((-40) - (y position)) * (0.8))//0 and -40 are the desired x and y positions of the player.
...//The basic platformer script goes here.
end

define Scroll (x) (y)//This goes in the player sprite.
change [level x v] by (round (x))//Round the variables so the level moves correctly.
change [level y v] by (round (y))
change x by (round (x))//When the level moves, the player must move with it.
change y by (round (y))

when green flag clicked//This goes in the ground sprite.
forever
go to x:(level x) y:(level y)
end
</scratchblocks>

== See Also ==
* [[How to Make a Basic Platformer]]
* [[Advanced Platformer Physics]]

[[Category:Scripting Tutorials]]
[[Category:Game Design Tutorials]]