ADR-0003 · accepted

Every genre runs on the runtime's fixed-step clock

Amended by ADR-0010 on 2026-11-04: the fixed clock, the 0.25 s clamp and the backlog drop live in GameLoop's { seconds } frames, { steps } frames are the no-drop path lockstep needs, and alpha is gone.

Amended by ADR-0012 on 2026-11-04: a lockstep run steps only on { steps } budgets, a step waits for its inputs and is never dropped, and a hidden tab stalls every player until the host removes it.

Amended on 2026-11-06: GameDriver is gone. The requestAnimationFrame loop below is now makeGameEngine's attach, which steps GameLoop by { seconds } frames (see the note on ADR-0010).

The runtime has one time model: GameDriver advances a run in fixed steps, 1/60 s by default, using core's FixedStepClock in a requestAnimationFrame loop. Fixed steps make a run behave the same on any screen and keep it deterministic. Turn-based genres use the same clock and count steps: push-puzzle takes at most one turn per step, ignores dt, and times hold-to-repeat in steps, so its replays are exact (finding 10).

Considered Options

• A turn-based time mode in the runtime, which #4 left for its own issue if the findings called for one. Finding 10 found no need. The fixed clock costs push-puzzle a call to step 60 times a second, and most of those steps hold no turn. The real frictions were elsewhere: sample (ADR-0005) and the view (finding 12).

Consequences

• A turn-based genre times things in steps. A held direction in push-puzzle moves on the press, again after 12 steps, then every 6. Repeat in the input layer would run on wall-clock time and break replays (finding 13).
• GameView.render's alpha means little to a genre that jumps a cell per turn. Push-puzzle's view slides each move over real time.
• The clock throws time away on purpose. The driver counts at most 0.25 s per frame, and the clock drops its backlog after five catch-up steps. A hidden tab gets no frames, so its run pauses.
• #25 revisits this. Lockstep runs step N once every player's input for step N has arrived, and it can never drop a step. #25 expects a timer-driven step loop, or a Worker, with requestAnimationFrame only for drawing.