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Physics layers and masks can be
a bit difficult to understand.

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So we made this little demo where you can
toggle them on different physics bodies

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to see how they work.

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First, you can find the demo
by pressing Ctrl + Shift + O

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and you look for LayersMasksDemo.tscn.

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Then press F6 to run it,

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and I want to run you through
some examples here.

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Let's start with the player and the rock
that you can see in the right column.

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When I move towards the rock,
the character is going to push it.

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Now, this is because the player has
the mask number 2

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and rock has the layer number 2.

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If I turn off the mask number 2
on the player,

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I now pass through the rock.

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I can restore the mask to push the rock.

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Then if I remove layer two from the rock,
I pass through it again.

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Why?

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Because I mask layer two on the player,
but the rock is on no layer,

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so nothing can collide with it.

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What if this time
I turn on mask one on the rock?

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The player is on physics layer one.

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Well, then my player can
push the rock again.

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So you can see how the mask allows for
an interaction between two physics bodies.

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As long as one has a layer and the other
has a matching mask,

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they are going to collide.

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It works this way in Godot 3.

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Similarly, here, we have a switch
that toggles the door open

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when it's being pressed.

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The switch is on layer three
and it masks layer one and two.

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If I turn off the layer three here,
the door closes.

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Why?

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Because our rock has mask three.

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This is what allows it
to detect the switch.

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So if I turn on layer three,
the switch gets pressed, the door opens.

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If I turn off layer three,
the door closes.

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Similarly, if I have a layer three,
but I turn off mask three on the rock,

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the door closes.

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But the switch has
its mask to one and two.

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This allows it to detect
the player walking

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on the switch right now.

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If I put the rock on layer one
or on layer two,

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the door opens accordingly.

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Similarly, with a pickup,
the pickup is on layer four,

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if I go back to the player,
turn off mask four,

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I can't pick up the gems.

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But if I turn the mask four back on,
I can now collect the gems.

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So I invite you to play
a bit with this demo.

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Hopefully, the demonstration helps to make
a little more sense of how these work.

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And by switching the things,

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you should get
a more intuitive understanding

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of these two confusing properties.

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With that, I'll see you in the next one.
Bye-bye.