/* ============================================
   CHAPTER 2: TRACE
   Theme: Something catches. The eye looking at the same geometry.
   Scope: body[data-chapter="trace"]
   ============================================ */

body[data-chapter="trace"] {
    --trace-bg: #06070A;
    --trace-surface: #0E1017;
    --trace-cyan: #00F0FF;
    --trace-magenta: #FF4FA3;
    --trace-lavender: #B28BFF;
    --trace-yellow: #FFE600;
    --trace-ink: #D8DBE2;
    --trace-mute: #5A5F6E;
    --trace-border: rgba(216, 219, 226, 0.12);

    background: var(--trace-bg);
    color: var(--trace-ink);
    overflow-y: auto;
    overflow-x: hidden;
}

/* 微妙な環境グラデーション */
body[data-chapter="trace"]::before {
    content: "";
    position: fixed;
    inset: 0;
    pointer-events: none;
    z-index: 0;
    background:
        radial-gradient(ellipse at 50% 20%, rgba(0, 240, 255, 0.03) 0%, transparent 60%),
        radial-gradient(ellipse at 80% 80%, rgba(178, 139, 255, 0.02) 0%, transparent 50%);
}

.chapter-trace {
    position: relative;
    width: 100%;
    z-index: 1;
}

/* ============================================
   INTRO BEAM: 最初の30秒体験
   ============================================ */
.trace-intro {
    position: relative;
    width: 100%;
    height: 100vh;
    height: 100dvh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    overflow: hidden;
}

.intro-beam-wrap {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.intro-beam-canvas {
    width: 100%;
    height: 100%;
    display: block;
}

.trace-intro-meta {
    position: absolute;
    bottom: clamp(4rem, 8vh, 6rem);
    left: var(--gutter);
    display: flex;
    align-items: center;
    gap: 1em;
    font-family: 'JetBrains Mono', monospace;
    font-size: var(--size-meta);
    letter-spacing: 0.28em;
    color: var(--trace-mute);
    text-transform: uppercase;
    animation: traceMetaFade 1800ms cubic-bezier(0.2, 0.8, 0.2, 1) 600ms both;
}

.trace-intro-meta .meta-index {
    color: var(--trace-cyan);
    font-weight: 500;
}

.trace-intro-meta .meta-divider {
    display: inline-block;
    width: 24px;
    height: 1px;
    background: var(--trace-mute);
}

.scroll-indicator {
    position: absolute;
    bottom: clamp(1.5rem, 3vh, 2.5rem);
    left: 50%;
    transform: translateX(-50%);
    width: 1px;
    height: 48px;
    background: rgba(216, 219, 226, 0.15);
    overflow: hidden;
}

.scroll-line {
    display: block;
    width: 100%;
    height: 100%;
    background: var(--trace-cyan);
    transform: translateY(-100%);
    animation: scrollDrop 2.4s cubic-bezier(0.65, 0, 0.35, 1) infinite;
}

@keyframes traceMetaFade {
    from { opacity: 0; transform: translateY(10px); }
    to   { opacity: 1; transform: translateY(0); }
}

@keyframes scrollDrop {
    0%   { transform: translateY(-100%); opacity: 0; }
    30%  { opacity: 1; }
    70%  { opacity: 1; }
    100% { transform: translateY(100%); opacity: 0; }
}

/* ============================================
   OBSERVATIONS: 1画面1対象
   ============================================ */
.observations-container {
    display: flex;
    flex-direction: column;
    gap: clamp(4rem, 10vh, 8rem);
    padding-bottom: clamp(5rem, 12vh, 9rem);
}

.observation-section {
    position: relative;
    min-height: 90vh;
    min-height: 90dvh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    padding: clamp(2rem, 5vh, 4rem) var(--gutter);
}

.observation-frame {
    position: relative;
    width: min(1040px, 90vw);
    aspect-ratio: 16 / 9;
    background: var(--trace-surface);
    border: 1px solid var(--trace-border);
    box-shadow: 0 20px 50px rgba(0, 0, 0, 0.45);
    overflow: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
}

.observation-canvas {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    display: block;
}

.observation-media {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
    opacity: 0.9;
    filter: contrast(1.05) brightness(0.95);
    transition: opacity 400ms ease;
}

.observation-overlay-grid {
    position: absolute;
    inset: 0;
    pointer-events: none;
    border: 1px solid rgba(216, 219, 226, 0.05);
}

/* 四隅の控えめなマーク */
.obs-corner {
    position: absolute;
    width: 8px;
    height: 8px;
    border-color: rgba(216, 219, 226, 0.3);
    pointer-events: none;
}
.obs-corner--tl { top: 8px; left: 8px; border-top: 1px solid; border-left: 1px solid; }
.obs-corner--tr { top: 8px; right: 8px; border-top: 1px solid; border-right: 1px solid; }
.obs-corner--bl { bottom: 8px; left: 8px; border-bottom: 1px solid; border-left: 1px solid; }
.obs-corner--br { bottom: 8px; right: 8px; border-bottom: 1px solid; border-right: 1px solid; }

.observation-caption {
    width: min(1040px, 90vw);
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    margin-top: 1rem;
    padding: 0 0.25rem;
}

.obs-tag {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.72rem;
    letter-spacing: 0.22em;
    color: var(--trace-cyan);
    text-transform: uppercase;
}

.obs-title {
    font-family: var(--font-body);
    font-size: 0.8rem;
    letter-spacing: 0.16em;
    color: var(--trace-mute);
    text-transform: uppercase;
}

/* ============================================
   TRACE FOOTER / NEXT CHAPTER
   ============================================ */
.trace-footer {
    position: relative;
    width: 100%;
    padding: clamp(3rem, 8vh, 6rem) var(--gutter) clamp(4rem, 10vh, 7rem);
    border-top: 1px solid var(--trace-border);
    background: rgba(6, 7, 10, 0.8);
}

.trace-footer-inner {
    width: min(1040px, 90vw);
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    flex-wrap: wrap;
    gap: 2rem;
}

.trace-summary {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.sum-num {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    letter-spacing: 0.2em;
    color: var(--trace-mute);
}

.sum-text {
    font-family: var(--font-body);
    font-size: clamp(1rem, 1.6vw, 1.3rem);
    font-weight: 300;
    letter-spacing: 0.08em;
    color: var(--trace-ink);
}

/* ============================================
   RESPONSIVE
   ============================================ */
@media (max-width: 860px) {
    .observation-frame {
        aspect-ratio: 4 / 3;
    }
}

@media (max-width: 720px) {
    .trace-intro-meta {
        bottom: 3.5rem;
        font-size: 0.65rem;
        letter-spacing: 0.2em;
    }

    .observation-section {
        padding: 1.5rem var(--gutter);
        min-height: auto;
        padding-top: 4rem;
    }

    .observation-frame {
        width: 100%;
        aspect-ratio: 1 / 1;
    }

    .observation-caption {
        width: 100%;
        font-size: 0.68rem;
    }

    .trace-footer-inner {
        flex-direction: column;
        align-items: flex-start;
        gap: 1.5rem;
    }
}

@media (prefers-reduced-motion: reduce) {
    .scroll-line { animation: none; transform: translateY(0); }
    .trace-intro-meta { animation: none; opacity: 1; }
}