idle fleet slows world clock to real time instead of freezing (ISS-128)

lib/useSimClock.ts

@@ -2,15 +2,16 @@
 
 import { useEffect, useRef, useState } from 'react';
 import type { StateSnapshot } from './game/state';
-import { WORLD_TIME_SCALE } from './worldClock';
+import { IDLE_WORLD_TIME_SCALE, WORLD_TIME_SCALE } from './worldClock';
 
 // ISS-007 (v0.16.1): the sim clock ticks smoothly on the CLIENT between polls instead of
 // jumping once per snapshot. The server's authoritative rate is exactly real-time × scale
 // (tickOnce in lib/sim/engine.ts: advance = min(elapsed, MAX_TICK_ELAPSED_MS) × timeScale), so
 // client-side extrapolation mirrors the server's own model. Every new snapshot re-anchors to
 // server truth, bounding any drift by network latency only. ISS-117 (v0.52.0): the scale is the
-// fixed WORLD_TIME_SCALE and the clock freezes while nothing is happening — mirroring the
-// server's idle-pause instead of a player-controlled pause.
+// fixed WORLD_TIME_SCALE; ISS-128 (v0.56.0): while nothing is happening it slows to
+// IDLE_WORLD_TIME_SCALE (real time) instead of freezing — mirroring the server's idle slowdown,
+// so polls re-anchor without a visible jump.
 
 export interface SimClockAnchor {
   // Server truth at anchor time — the snapshot's simState.clockMs.
@@ -22,11 +23,11 @@ export interface SimClockAnchor {
 }
 
 // Pure core of the extrapolation — mirrors tickOnce: while advancing, game time advances by
-// real-time × WORLD_TIME_SCALE; while idle it is frozen (advance 0). nowMs before `at` clamps to
-// the anchor value instead of going backwards. Unit-testable in node.
+// real-time × WORLD_TIME_SCALE; while idle it slows to real-time × IDLE_WORLD_TIME_SCALE (ISS-128).
+// nowMs before `at` clamps to the anchor value instead of going backwards. Unit-testable in node.
 export function advanceSimClock(anchor: SimClockAnchor, nowMs: number): number {
-  if (!anchor.advancing) return anchor.clockMs;
-  return anchor.clockMs + Math.max(0, nowMs - anchor.at) * WORLD_TIME_SCALE;
+  const scale = anchor.advancing ? WORLD_TIME_SCALE : IDLE_WORLD_TIME_SCALE;
+  return anchor.clockMs + Math.max(0, nowMs - anchor.at) * scale;
 }
 
 // ~10 fps display refresh — smooth for a seconds-precision wall clock without busy re-renders.
@@ -41,8 +42,8 @@ export function useSimClock(snapshot: StateSnapshot | null): number | null {
   // (useGameState), so this runs once per poll cycle as well.
   useEffect(() => {
     if (!snapshot) return;
-    // Mirror of the server's shouldAdvanceTime (lib/sim/engine.ts): frozen while no plane is
-    // flying or in repair. One line on purpose — keep it in sync with that function.
+    // Mirror of the server's shouldAdvanceTime (lib/sim/engine.ts): full rate only while a plane
+    // is flying or in repair, idle real-time otherwise. One line on purpose — keep it in sync.
     const advancing = snapshot.planes.some((p) => p.status === 'flying' || p.status === 'repairing');
     anchorRef.current = { clockMs: snapshot.simState.clockMs, at: Date.now(), advancing };
     setDisplayMs(advanceSimClock(anchorRef.current, Date.now()));