I'm making a pen game on scratch and I don't know how to add collision…

What exactly are you trying to get collision with?
Lines?
Shapes?
Drawings?

MathPuppy314 wrote:

What exactly are you trying to get collision with?
Lines?
Shapes?
Drawings?

The walls and coins.
It's not a platformer, too.

You can use the touching color sensing block to detect collision.

<touching color [#b036c9] ?>
<color [#214635] is touching [#820756] ?>

If you don't want to rely on colors and if your walls are rectangular you can use AABB collision. and for circular things such as coins, you can compare distances and the radius of the object to detect collision. See https://developer.mozilla.org/en-US/docs/Games/Techniques/2D_collision_detection for some collision detection techniques.

Jman1111 wrote:

You can use the touching color sensing block to detect collision.

<touching color [#b036c9] ?>
<color [#214635] is touching [#820756] ?>

~snip~

Those blocks will not work for 100% pen. They both use the sprite costume to detect colors.

MathPuppy314 wrote:

Jman1111 wrote:

You can use the touching color sensing block to detect collision.

<touching color [#b036c9] ?>
<color [#214635] is touching [#820756] ?>

~snip~

Those blocks will not work for 100% pen. They both use the sprite costume to detect colors.

So then hooooowwwww

The easiest way is to use AABB vs AABB collision (AABB means Axis Aligned Bounding Box which is basically a rectangle)

So when you draw a wall it must be axis aligned, and then represent player as AABB , now you can check collision between them.

To represent an AABB you'll need MinX , MaxX, MinY, MaxY.

So to check collision between them use

define AABB vs AABB collision  (minX1) (maxX1) (minY1) (maxY1) | (minX2) (maxX2) (minY2) (maxY2) 
set [collision v] to [0]
if <(minX1) < (maxX2)> then
if <(maxX1) > (minX2)> then
if <(minY1) < (maxY2)> then
if <(maxY1) > (minY2)> then
set [collision v] to [1]
end
end
end
end

And to define AABB from wall it's logical I think.
For player it can be:
minX=playerX
maxX=playerX+playerSize
minY=playerY
maxY=playerY+playerSize

ggenije wrote:

The easiest way is to use AABB vs AABB collision (AABB means Axis Aligned Bounding Box which is basically a rectangle)

So when you draw a wall it must be axis aligned, and then represent player as AABB , now you can check collision between them.

To represent an AABB you'll need MinX , MaxX, MinY, MaxY.

So to check collision between them use

define AABB vs AABB collision  (minX1) (maxX1) (minY1) (maxY1) | (minX2) (maxX2) (minY2) (maxY2) 
set [collision v] to [0]
if <(minX1) < (maxX2)> then
if <(maxX1) > (minX2)> then
if <(minY1) < (maxY2)> then
if <(maxY1) > (minY2)> then
set [collision v] to [1]
end
end
end
end

And to define AABB from wall it's logical I think.
For player it can be:
minX=playerX
maxX=playerX+playerSize
minY=playerY
maxY=playerY+playerSize

???

First tell me how do you draw walls and player?

Pen…
Player is:

define draw player
pen down

when green flag clicked
forever
clear
draw player
end

If you make the player a sprite you can use the color collision detection as I suggested before with the other things that you have drawn with the pen. But if you want 100% pen to work you will have to calculate the collision on your own using AABB collisions like @ggenije said, Circle collision by comparing radius and distances, or something else depending on the exact shape of your pen objects. If you refer to my previous post I posted a link that shows you those techniques. Rotated and shapes with many vertices a bit more tricky to calculate.

Bro Thats so cool