Hi

I want to learn a bit of how multiplayer works in gamedev. To do so I am making a simple platformer game with a coop feature. I don't really know where to start. I was thinking of a client-server architetcture, where first player creates the game and the second one joins it. The only thing client would do is sending input to the server and drawing. So all of the calculations would be done on the server side. But that seems strange to me.. any tips on how to implement networking in a 2D platformer?

Depending on the details of your game, if the server has to send the position of every object in the game to the client, this may end up being too much information and you may end up having performance problems.

If both players are running full versions of the game, the only thing they need to know from the other player is the precise sequence of inputs, so you could just communicate that.