Performance

This page sets out what has been measured of the app’s launch, its opponents, its animations and the danger search behind the music, and what each figure rests on.

Each measured figure says where it was measured: on the Vega Virtual Device (SDK 0.24.12112, 1920 x 1080, on an Apple silicon Mac) or in Node. Nothing here has been measured on a Fire TV Stick, and the Virtual Device’s timings are not a Stick’s.

Launch Key Performance Indicators (KPIs)

Amazon’s Measure App KPIs page for Vega 0.24 gives launch guidelines: time to first frame (TTFF) under 1.5 s for a cool start and under 0.5 s for a warm one, and time to fully drawn (TTFD) under 8.0 s cool and under 1.5 s warm.

The app reports the fully drawn marker with useReportFullyDrawn from @amazon-devices/kepler-performance-api: once after its first render, which already shows the home screen, and again each time it comes back to active from the background or inactive state, which is a warm start. The OS measures time to first frame without a marker.

Measured on the Vega Virtual Device on 25 September 2026 with vega exec perf kpi-visualizer --kpi cool-start-latency on a Release build: the average of 3 cool starts, without --certification.

Metric	Measured (Virtual Device, 25 Sep 2026)	Amazon guideline, cool start
Time to first frame (TTFF)	309 ms	< 1.5 s
Time to fully drawn (TTFD)	748 ms	< 8.0 s

The run still ended in VALUE VALIDATION FAILED, because the validator counts an app with no network calls as a failure (FL-20). Warm start cannot be measured on the Virtual Device (FL-21); unit tests cover the warm-start report (native/test/soundApp.test.tsx). These figures predate the music, the voices and the portraits, and have not been re-measured since.

What the start does not wait for

1. No network calls. The app makes none, at launch or later: no sign-in, no telemetry, no remote assets. Its only fetch reads the music catalogue from its own package (file://).
2. Synchronous reads. Game state, the record of completed games and the settings are stored in @amazon-devices/react-native-mmkv. MMKV memory-maps the data file, so they are read synchronously during the first render.
3. No loading state. The saved game and the settings are there before the first frame, so the app draws no spinner or splash of its own, and its first frame is the home screen, ready for the remote. On the Virtual Device, an earlier version that rendered nothing until it had read storage never received remote input (FL-07).

Opponents’ decision time

Dice Chess TV offers three built-in opponents: Rolly (random), Grabby (greedy capture) and Rampage (aggressive king hunter). Each is an algorithm of the engine, asked for a whole turn through getBestMove, and all three run on the device, on the JavaScript thread.

A probe build on the Vega Virtual Device timed Grabby’s and Rampage’s decisions on 26 September 2026, and Node timed 100 games of each. The figures are the slowest seen, not bounds:

Opponent	How it plays	Slowest in Node (100 games)	Slowest on the Virtual Device	Wait before each step
Rolly	Any legal turn, at random	not timed	not timed	600 ms
Grabby	Takes the most valuable piece it can	48 ms	155 ms, over 14 turns	600 ms
Rampage	Hunts pieces, pushes its pawns and goes for the king	38 ms	339 ms, over about two games, on a first roll	600 ms

Pacing

Each step of the opponent’s turn (the roll, each action, the handoff) waits 600 ms (BOT_STEP_MS in native/src/screen.ts), so a player can follow it from the sofa. The wait comes first. At the step of its first action, the opponent then decides its whole turn at once, on the JavaScript thread, so the decision time adds to that step: Rampage’s slowest decision on the Virtual Device, 339 ms, added about a third of a second to it. No separate thread is used.

How to run a stronger opponent off the JavaScript thread is open (FL-13): React Native has no Web Worker, an app has no documented way to start a Vega headless task, and @amazon-devices/react-native-worklets is an untested candidate.

Danger Evaluation & Threat Analysis

The music follows the danger to a king. At the start of each turn, src/core/danger.ts measures how close a side is to taking the other’s king, and the music plays a calm, tense or critical theme, moving up at once and down one level per turn. Against the computer it measures the danger to the person’s king; in hotseat, the greater danger to either king.

• Critical: some roll would let the attacking side take the king with its first action. This takes one pseudo-legal move generation: a median of 0.08 ms over 61 engine positions, in a probe build on the Vega Virtual Device on 26 September 2026.
• Tense: at least 22 of the 216 ordered rolls (6 × 6 × 6) would let the attacking side take the king within its turn, in up to three actions. The search tries the 56 distinct rolls, each weighted by how many of the 216 it stands for, and stops once the answer is known.
• Calm: neither.

In the same probe, a search over the 56 rolls took a median of 427 ms and at most 1.6 s. That search stopped at the first roll able to take the king; the app’s search counts rolls until the threshold is settled either way. A search that long, run at once, would hold up the JavaScript thread, so useDanger.ts advances the search one roll per step, each step scheduled with setTimeout(step, 0), and a key press can be handled between steps. A key press that arrives during a step still waits for that roll’s search to finish; how long one step takes has not been measured on its own. In play on the Virtual Device on 26 September 2026, a turn’s search took 0.5–2 s of wall time from start to answer, and a critical answer 18–30 ms.

UI Motion & Animation Performance

Every animation uses Animated.timing with React Native’s native driver (useNativeDriver: true). React Native for Vega’s Animated page says the native driver sends an animation to native code before it starts, so once it is running a busy JavaScript thread does not affect it. We have not tested that on its own.

Animation	Duration	Implementation Details
Piece Move Slide	220 ms	Eased out, from the old square to the new one. On the Virtual Device on 27 September 2026, a knight’s capture took 224 ms over 11 captured frames. A unit test keeps it at 300 ms or less, a ceiling the project chose; Amazon’s Fire TV design guidelines give no duration.
Dice Roll Tumble	260 ms	Each die turns and grows onto its face in 200 ms, starting 30 ms after the die on its left. A die no legal turn can spend dims once the tumble is over. On the Virtual Device on 29 September 2026, a roll took about 260 ms.
Menu Focus State	No transition	The focused item is framed in cyan over a faint fill. While OK is held, it fills more strongly and is drawn at 97 % of its size. This is a style change, not an animation.

Accessibility: Reduced Motion

useReducedMotion.ts asks AccessibilityInfo.isReduceMotionEnabled and listens for reduceMotionChanged. When the answer is yes, and until an answer arrives, pieces are drawn on their new squares without sliding, the dice appear without tumbling, and the board turns without fading. React Native for Vega 0.83’s AccessibilityInfo page lists neither the query among its implemented methods nor the event among its events. On the Vega Virtual Device the query answers false and there is no setting to change it, so only unit tests cover the reduced-motion branch. Whether a Fire TV Stick offers the setting is not yet checked.

Physical Device Verification Roadmap

Every device figure above comes from the Vega Virtual Device. None has been measured on a Fire TV Stick (32-bit armv7, models AFTCA002 and AFTCL001). On a Stick, these checks are still to come:

• Measuring the warm-start KPIs, which the Virtual Device cannot (FL-21), and the cool start again.
• Checking that a slide stays smooth, and timing the opponents’ decisions and the danger search.
• Checking the safe area on a television with overscan, and whether the Stick offers a reduced-motion setting.