multiplayer questions

Hey guys i’m guessing you guys get this a lot but i’m trying to understand the considerations and the aspects of the game that need to be taken into account for multiplayer. From what i’ve been googling and if i get this right. The reason why multiplayer needs to be worked on at the start is because lets say in the aspect of blueprints. Now that multiplayer is part of the game, the game needs to send all kinds of infomation to the server to determine positioning and subsequent actions?

So lets say player 1 casts a spell on player 2. In a singleplayer instance we would just create the spell on event player presses “1”, spawn projectile at a certain velocity > if player 2 gets hit. 50 hp removed from player 2. But in multiplayer each of these steps need to be feedbacked to the server so that the server can decide and make confirmations that the spell was indeed cast, player 2 was hit and 50 hp has been deducted as a consequence.

With that said, am i right to say that every fundamental mechanic that is made in single player context will have to be reworked with a way to feedback to the server and missing these inputs will lead to complications?

I’m guessing there is much more than that. But i would like to confirm if I have understood it right that for everything that occurs in a multiplayer game it needs a way to feedback to the server to award penalties and acknowledge changes. I’m really new to this but i would like to set my understanding straight

That’s correct, when building a multiplayer system you have to take those things into account in your gameplay. Besides that, you also have to consider how multiplayer affects performance.

Noted, in that case say if i have a single player mode and multiplayer mode. For the instance of the spell above. Would i have to make 2 seperate bps, one that does not account server feedback for singleplayer and another that does for multiplayer? Or would it be better to have them in the same blueprint but create a BOL to check what mode the player has chosen and if they have chosen multiplayer to globally activate all required multiplayer variables to be accounted for. Not sure if that is possible.