/* ============================================
   CHAPTER 1: GEOMETRIC PULSE
   Harmonograph-based mathematical art.
   Scope: body[data-chapter="intro"] 配下のみ
   ============================================ */

body[data-chapter="intro"] {
    --intro-bg: #05060A;
    --intro-cyan: #00F0FF;
    --intro-magenta: #FF4FA3;
    --intro-lavender: #B28BFF;
    --intro-yellow: #FFE600;
    --subtitle-ink: #D6D9E0;
    --subtitle-mute: #6A6E78;

    background: var(--intro-bg);
}

/* 背景のごく僅かなビネット */
body[data-chapter="intro"]::before {
    content: "";
    position: fixed;
    inset: 0;
    pointer-events: none;
    z-index: 0;
    background:
        radial-gradient(ellipse at 50% 45%,
            rgba(40, 60, 110, 0.18) 0%,
            rgba(5, 6, 10, 0) 55%),
        radial-gradient(ellipse at 50% 100%,
            rgba(255, 79, 163, 0.06) 0%,
            rgba(5, 6, 10, 0) 40%);
}

.chapter-intro {
    position: relative;
    width: 100%;
    min-height: 100vh;
    min-height: 100dvh;
    overflow: hidden;
    isolation: isolate;
}

/* ---- Harmonograph 二層 Canvas ---- */
.harmonograph {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    display: block;
    opacity: 0;
    animation: harmonographFadeIn 2200ms cubic-bezier(0.2, 0.8, 0.2, 1) 200ms forwards;
}
.harmonograph--trail { z-index: 1; }
.harmonograph--pen {
    z-index: 2;
    pointer-events: none;
    filter: saturate(1.1);
}
@keyframes harmonographFadeIn {
    from { opacity: 0; }
    to   { opacity: 1; }
}

/* ---- 四隅ティックは削除 ---- */
.stage-ticks {
    display: none;
}

/* ============================================
   SUBTITLE
   ============================================ */
.subtitle {
    position: absolute;
    left: var(--gutter);
    right: var(--gutter);
    bottom: clamp(2.5rem, 5vw, 4rem);
    z-index: 4;
    color: var(--subtitle-ink);
    animation: subtitleRise 1400ms cubic-bezier(0.2, 0.8, 0.2, 1) 900ms both;
}
@keyframes subtitleRise {
    from { opacity: 0; transform: translateY(14px); }
    to   { opacity: 1; transform: translateY(0); }
}

.sub-row {
    display: flex;
    align-items: center;
    gap: 1em;
    font-family: var(--font-body);
    font-size: 0.72rem;
    letter-spacing: 0.3em;
    text-transform: uppercase;
    color: var(--subtitle-mute);
}
.sub-row--top { margin-bottom: 0.75rem; }

.sub-index {
    font-family: 'JetBrains Mono', monospace;
    color: var(--intro-cyan);
    letter-spacing: 0.1em;
    font-weight: 500;
}
.sub-divider {
    display: inline-block;
    width: 28px;
    height: 1px;
    background: var(--subtitle-mute);
}
.sub-kicker {
    color: var(--subtitle-ink);
    font-style: normal;
}

.sub-title {
    font-family: var(--font-display);
    font-weight: 400;
    font-size: clamp(2.2rem, 6vw, 5rem);
    line-height: 0.92;
    letter-spacing: 0.02em;
    color: var(--subtitle-ink);
    text-transform: uppercase;
    margin-bottom: 0.9rem;
}
.sub-title-main {
    display: inline-block;
    position: relative;
}
.sub-title-main::before {
    content: "";
    position: absolute;
    left: -0.7em;
    top: 50%;
    width: 0.35em;
    height: 0.35em;
    transform: translateY(-50%);
    background: var(--intro-cyan);
    box-shadow: 0 0 12px rgba(0, 240, 255, 0.9),
                0 0 24px rgba(0, 240, 255, 0.5);
}

.sub-row--bot {
    justify-content: flex-start;
    flex-wrap: wrap;
    gap: 0.5em 1.5em;
}
.sub-byline em {
    font-style: normal;
    color: var(--intro-magenta);
    letter-spacing: 0.22em;
    font-weight: 500;
}

.formula-center {
    position: absolute;
    left: 50%;
    top: 54%;
    transform: translate(-50%, -50%);
    z-index: 3;
    pointer-events: none;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.68rem;
    letter-spacing: 0.08em;
    color: var(--subtitle-mute);
    text-transform: none;
    white-space: nowrap;
}
.formula-center sup {
    font-size: 0.7em;
    vertical-align: super;
}

/* ============================================
   CONTROL PANEL (PC / Tablet)
   ============================================ */
.controls {
    position: absolute;
    right: var(--gutter);
    bottom: clamp(2.5rem, 5vw, 4rem);
    z-index: 5;
    width: 240px;
    max-width: calc(100vw - var(--gutter) * 2);
    color: var(--subtitle-ink);
    font-family: var(--font-body);
    animation: subtitleRise 1400ms cubic-bezier(0.2, 0.8, 0.2, 1) 1400ms both;
}

.controls-head {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-bottom: 0.6rem;
    margin-bottom: 0.75rem;
    border-bottom: 1px solid rgba(214, 217, 224, 0.12);
    cursor: pointer;
}

.controls-title {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.62rem;
    letter-spacing: 0.3em;
    color: var(--subtitle-mute);
    text-transform: uppercase;
}

.controls-toggle {
    width: 18px;
    height: 18px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    transition: transform 240ms var(--ease-cut);
}

.toggle-icon {
    width: 9px;
    height: 9px;
    border-right: 1px solid var(--subtitle-ink);
    border-bottom: 1px solid var(--subtitle-ink);
    transform: rotate(45deg);
    transition: transform 240ms var(--ease-cut);
}

.controls[data-collapsed="true"] .toggle-icon {
    transform: rotate(-135deg);
}

.controls[data-collapsed="true"] .controls-body {
    max-height: 0;
    opacity: 0;
    overflow: hidden;
    pointer-events: none;
    margin: 0;
}

.controls-body {
    display: flex;
    flex-direction: column;
    gap: 0.85rem;
    max-height: 400px;
    opacity: 1;
    transition: max-height 320ms var(--ease-cut), opacity 240ms var(--ease-cut);
}

.control-row {
    display: flex;
    flex-direction: column;
    gap: 0.35rem;
}

.control-label {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    font-size: 0.62rem;
    letter-spacing: 0.22em;
    color: var(--subtitle-mute);
    text-transform: uppercase;
}

.control-value {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.68rem;
    letter-spacing: 0.04em;
    color: var(--intro-cyan);
    text-transform: none;
}

/* ---- Slider ---- */
.slider {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 1px;
    background: rgba(214, 217, 224, 0.22);
    cursor: pointer;
    outline: none;
    padding: 0;
    margin: 0.25rem 0;
}
.slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 10px;
    height: 10px;
    background: var(--intro-cyan);
    border: none;
    cursor: grab;
    box-shadow: 0 0 8px currentColor;
    transition: transform 140ms var(--ease-cut), background 240ms;
}
.slider::-webkit-slider-thumb:hover { transform: scale(1.3); }
.slider::-webkit-slider-thumb:active { cursor: grabbing; transform: scale(1.1); }
.slider::-moz-range-thumb {
    width: 10px;
    height: 10px;
    background: var(--intro-cyan);
    border: none;
    cursor: grab;
    box-shadow: 0 0 8px currentColor;
}
.slider::-moz-range-track {
    height: 1px;
    background: rgba(214, 217, 224, 0.22);
}

/* ---- Palette Picker ---- */
.palette-row {
    display: grid;
    grid-template-columns: repeat(6, minmax(0, 1fr));
    gap: 0.35rem;
    width: 100%;
    margin-top: 0.25rem;
}
.palette-btn {
    position: relative;
    width: 100%;
    min-width: 0;
    height: 22px;
    padding: 0;
    cursor: pointer;
    background: transparent;
    opacity: 0.55;
    transition: opacity 200ms var(--ease-cut), transform 200ms var(--ease-cut);
}
.palette-btn:hover { opacity: 0.9; transform: translateY(-1px); }
.palette-btn.is-active { opacity: 1; }
.palette-btn.is-active::after {
    content: "";
    position: absolute;
    left: 0;
    right: 0;
    bottom: -5px;
    height: 1px;
    background: var(--intro-cyan);
    box-shadow: 0 0 6px currentColor;
}
.palette-swatch {
    display: block;
    width: 100%;
    height: 100%;
    background: linear-gradient(
        90deg,
        var(--a) 0%, var(--a) 33%,
        var(--b) 33%, var(--b) 66%,
        var(--c) 66%, var(--c) 100%
    );
}
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0,0,0,0);
    white-space: nowrap;
    border: 0;
}

/* ---- Tablet ---- */
@media (max-width: 860px) {
    .controls {
        bottom: auto;
        top: calc(var(--nav-top) + 6rem);
        right: var(--gutter);
        width: 220px;
    }
}

/* ============================================
   MOBILE: Full-width Bottom Bar Controls
   ============================================ */
@media (max-width: 720px) {
    .sub-row {
        font-size: 0.62rem;
        letter-spacing: 0.22em;
    }

    .sub-title {
        font-size: clamp(1.8rem, 9vw, 3rem);
    }

    .formula-center {
        top: 58%;
        font-size: 0.62rem;
    }

    .subtitle {
        bottom: calc(5.5rem + env(safe-area-inset-bottom, 0px));
    }

    .controls {
        position: fixed;
        left: 0;
        right: 0;
        top: auto;
        bottom: 0;
        width: 100%;
        max-width: none;
        transform: none;
        z-index: 8500;
        padding:
            0.55rem
            max(1rem, env(safe-area-inset-right, 0px))
            calc(0.8rem + env(safe-area-inset-bottom, 0px))
            max(1rem, env(safe-area-inset-left, 0px));
        border-top: 1px solid rgba(214, 217, 224, 0.08);
        background: rgba(10, 12, 18, 0.58);
        backdrop-filter: blur(14px) saturate(1.08);
        -webkit-backdrop-filter: blur(14px) saturate(1.08);
        box-shadow: 0 -10px 30px rgba(0, 0, 0, 0.28);
    }

    .controls::before {
        content: "";
        position: absolute;
        left: 50%;
        top: 0.3rem;
        transform: translateX(-50%);
        width: 42px;
        height: 4px;
        border-radius: 999px;
        background: rgba(214, 217, 224, 0.34);
        box-shadow: 0 0 10px rgba(214, 217, 224, 0.06);
        pointer-events: none;
    }

    .controls-head {
        position: relative;
        display: block;
        margin-bottom: 0;
        padding: 0.65rem 0 0;
        border-bottom: 0;
        min-height: 32px;
        text-align: center;
        cursor: pointer;
    }

    .controls-title {
        display: block;
        width: 100%;
        font-size: 0.58rem;
        letter-spacing: 0.24em;
        color: var(--subtitle-ink);
        opacity: 0.9;
        text-align: center;
    }

    .controls-toggle {
        position: absolute;
        right: 0;
        top: 50%;
        transform: translateY(-50%);
        width: 20px;
        height: 20px;
        display: inline-flex;
        align-items: center;
        justify-content: center;
        pointer-events: none;
    }

    .toggle-icon {
        width: 8px;
        height: 8px;
        opacity: 0.92;
    }

    .controls[data-collapsed="true"] .toggle-icon {
        transform: rotate(-135deg);
    }

    .controls-body {
        margin-top: 0.7rem;
        padding-top: 0.75rem;
        border-top: 1px solid rgba(214, 217, 224, 0.10);
        max-height: 320px;
        overflow: hidden;
        transform: translateY(0);
        transition:
            max-height 320ms var(--ease-cut),
            opacity 240ms var(--ease-cut),
            transform 320ms var(--ease-cut),
            margin-top 240ms var(--ease-cut),
            padding-top 240ms var(--ease-cut);
    }

    .controls[data-collapsed="true"] .controls-body {
        max-height: 0;
        opacity: 0;
        overflow: hidden;
        pointer-events: none;
        margin-top: 0;
        padding-top: 0;
        border-top-color: transparent;
        transform: translateY(10px);
    }

    .controls[data-collapsed="true"] {
        padding-bottom: calc(0.55rem + env(safe-area-inset-bottom, 0px));
    }

    .control-row {
        gap: 0.42rem;
    }

    .control-label {
        font-size: 0.58rem;
        letter-spacing: 0.18em;
    }

    .control-value {
        font-size: 0.64rem;
    }

    .slider {
        margin: 0.35rem 0 0.2rem;
    }

    .palette-row {
        gap: 0.28rem;
    }

    .palette-btn {
        height: 20px;
    }

    .palette-btn.is-active::after {
        bottom: -4px;
    }
}