Turning a regular game timer into a sequence to experiment with looking at the game loop as something that iterates the timer sequence instead of an imperative while loop.

Timer.fsx

module Timer

open System.Diagnostics

type TimeInfo =
    { TotalElapsed: float
      Delta: float }

let start () =
    let last =
        ref { TotalElapsed = 0.
              Delta = 0. }

    let watch =
        Stopwatch.StartNew ()
    
    seq {
        let totalElapsed =
            watch.Elapsed.TotalMilliseconds
        
        let last' = !last
        
        last := { TotalElapsed = totalElapsed
                  Delta = totalElapsed - last'.TotalElapsed }

        yield !last }

Just a quick jot of a thought, nothing more.