How Scoring Works

🎨 Color — CIEDE2000

Your color score is not based on simple RGB distance. We measure how different two colors look to the human eye using the CIEDE2000 formula.

The Pipeline

1. HSB → RGB: Both your pick and the target start in HSB space. We convert to RGB as an intermediate step.
2. RGB → Lab: RGB values are transformed into CIELAB color space through linearization and chromatic adaptation. Lab is perceptually uniform.
3. CIEDE2000 (ΔE₀₀): Calculates perceptual distance accounting for hue rotation, chroma weighting, and lightness sensitivity.
4. ΔE₀₀ → Score (0–10): Mapped via sigmoid curve. ΔE₀₀ = 0 (perfect match) gives 10.00.

Adjustments

• Hue Recovery: Correct hue family (within 25°) earns a small bonus.
• Hue Penalty: Hue off by 30°+ on a saturated color loses a fraction.

Easy vs Hard

Easy mode uses moderate saturation/brightness (40–90%). Hard mode includes very desaturated and dark colors — significantly harder to recall.

🔊 Sound — ERB Psychoacoustic Model

Your sound score uses an ERB (Equivalent Rectangular Bandwidth) psychoacoustic model — the same perceptual framework used in hearing research.

The Pipeline

1. Frequency → ERB-rate: Both the target and your pick are converted from Hz to ERB-rate using: 21.4 × log₁₀(1 + 0.00437 × f). This approximates how the human cochlea perceives pitch.
2. Perceptual Distance: The absolute ERB-rate difference is normalized against the total playable frequency range.
3. Dual Gaussian Scoring: We use two Gaussian curves — a sharp one (rewarding near-perfect matches) and a gentle one (giving partial credit). Your score is the higher of the two, mapped to 0–10.

Why ERB?

Human pitch perception is logarithmic, not linear. The difference between 200 Hz and 400 Hz sounds the same as 400 Hz vs 800 Hz — both are one octave. ERB-rate captures this nonlinearity, so your score reflects how different two tones sound, not how far apart their frequencies are in Hz.

Easy vs Hard

In Easy mode, the Hz display is visible while you tune. Hard mode hides the frequency readout — you must rely purely on your ears.