I am developing a multiplayer game (for scientific experiment) where participants engage in 20 rounds of interactive decision making. Each round has 3 stages, each should last maximum for 30 seconds. I wonder what would be a good way to implement the countdown.
Currently, I am using a client side approach. On the creation of the round template, I use client side timer that submits the answer of the participant when it reaches 0. This is working fine so far (because everyone starts the game at the exact same time, and the next round starts only after everyone has submitted an answer). I am not sure that this is a good way to do it, considering that participants might disconnect (go offline, close the browser, have connectivity issues) and might manipulate the sessions or something.
Would it be a better approach to do a server side timer? For instance, a collection that contains the timer, and participants subscribe to that collection? If so, how would one implement a server-side countdown? Also, would this approach cause high demand on the server, given that every second in the countdown (that we display in the template) would require listening to data on the server?