I am planning to make a card game like Yu-Gi-Oh, and I want to make the P2 not able to see the cards in P1 hand and vice versa.
So I would like to know how can I make so the screen one player sees is different from another.
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Multiplayer plugin, check the manual
I looked up in the manual but couldn't find where it's saying about it, in which topic of it should I be looking at?
What you're describing is a multiplayer game, no? You need to build one, check out the example projects that come with Construct there are a few multiplayer game examples.
DiMinuto
I assume you're talking about a 2 player - online multiplayer scenario. Otherwise it might be difficult to hide cards from one-another when they look at the same screen.
So for a multiplayer scenario, all you have to do is to differentiate betwen Host and Peer. This should be fairly easy to do and is covered in the official examples and tutorials.
If Multiplayer-> is Host -> hide Peer cards.
Else -> hide Host cards.
Multiplayer Examples
https://editor.construct.net/#open=multiplayer-pong
https://editor.construct.net/#open=multiplayer-game
https://editor.construct.net/#open=multiplayer-chat
Multiplayer Tutorials
https://www.construct.net/en/courses/online-multiplayer-construct-12