:root {
    --ember: #c45e2c;
    --amber: #d4913a;
    --coral: #e07858;
    --abyss: #0a1a1f;
    --ocean-mid: #122a32;
    --surface-glass: #1a3a42;
    --text-primary: #d4e8e0;
    --text-muted: #7a9a90;
    --glow: #ff9e5e;
    --depth: 0;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-snap-type: y proximity;
    scroll-behavior: smooth;
}

body {
    background: var(--abyss);
    color: var(--text-primary);
    font-family: 'Nunito', sans-serif;
    font-weight: 400;
    font-size: clamp(1rem, 1.8vw, 1.15rem);
    line-height: 1.75;
    letter-spacing: 0.01em;
    overflow-x: hidden;
}

.center-line {
    position: fixed;
    top: 0;
    left: 50%;
    width: 1px;
    height: 100vh;
    background: var(--ember);
    opacity: 0.15;
    z-index: 100;
    pointer-events: none;
    transition: opacity 0.3s;
}

.depth-chamber {
    position: relative;
    min-height: 100vh;
    display: grid;
    place-items: center;
    overflow: hidden;
    scroll-snap-align: start;
}

.grid-overlay {
    position: absolute;
    inset: 0;
    background-image:
        linear-gradient(to right, rgba(122, 154, 144, 0.04) 1px, transparent 1px),
        linear-gradient(to bottom, rgba(122, 154, 144, 0.04) 1px, transparent 1px);
    background-size: 60px 60px;
    pointer-events: none;
}

.section-content {
    position: relative;
    z-index: 2;
    text-align: center;
    max-width: 900px;
    padding: 2rem;
}

.depth-marker {
    position: absolute;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.depth-marker::before,
.depth-marker::after {
    content: '';
    width: 40px;
    height: 1px;
    background: var(--text-muted);
    opacity: 0.4;
}

.depth-label {
    font-family: 'IBM Plex Mono', monospace;
    font-weight: 300;
    font-size: clamp(0.75rem, 1.2vw, 0.9rem);
    letter-spacing: 0.04em;
    color: var(--text-muted);
}

/* Section 1: Surface Layer */
.surface-layer {
    background: linear-gradient(180deg, var(--ocean-mid) 0%, var(--abyss) 100%);
}

.title {
    font-family: 'Nunito Sans', sans-serif;
    font-weight: 300;
    font-size: clamp(2.4rem, 6vw, 5.5rem);
    letter-spacing: 0.08em;
    line-height: 1.1;
    text-transform: uppercase;
    color: var(--text-primary);
    margin-bottom: 2rem;
}

.title .letter {
    display: inline-block;
    transition: transform 0.6s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.subtitle {
    font-family: 'IBM Plex Mono', monospace;
    font-weight: 300;
    font-size: clamp(0.75rem, 1.2vw, 0.9rem);
    letter-spacing: 0.04em;
    line-height: 1.6;
    color: var(--text-muted);
    max-width: 500px;
    margin: 0 auto;
    opacity: 0;
    transition: opacity 1.5s ease;
}

.subtitle.visible {
    opacity: 1;
}

.subtitle .char {
    opacity: 0;
    transition: opacity 0.05s ease;
}

.subtitle .char.revealed {
    opacity: 1;
}

/* Section 2: Sonar Chamber */
.sonar-chamber {
    background: var(--abyss);
}

.sonar-svg {
    width: min(80vw, 500px);
    height: min(80vw, 500px);
}

.sonar-ring {
    fill: none;
    stroke: var(--surface-glass);
    stroke-width: 1;
}

.sonar-ring-mid1 { opacity: 0.7; }
.sonar-ring-mid2 { opacity: 0.5; }
.sonar-ring-inner { opacity: 0.3; }

.sweep-line {
    stroke: var(--glow);
    stroke-width: 2;
    opacity: 0.8;
    transform-origin: 300px 300px;
    animation: sweep 12s linear infinite;
}

@keyframes sweep {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
}

.data-point {
    fill: var(--surface-glass);
    transition: fill 0.3s ease, filter 0.3s ease;
}

.data-point.active {
    fill: var(--glow);
    filter: drop-shadow(0 0 6px var(--glow));
}

.sonar-text {
    font-family: 'IBM Plex Mono', monospace;
    font-weight: 300;
    font-size: clamp(0.75rem, 1.2vw, 0.9rem);
    color: var(--text-muted);
    margin-top: 2rem;
    letter-spacing: 0.04em;
}

/* Section 3: Terrain Map */
.terrain-map {
    background: linear-gradient(180deg, var(--abyss) 0%, var(--ocean-mid) 100%);
}

.terrain-svg {
    width: min(90vw, 700px);
    height: auto;
}

.contour-line {
    fill: none;
    stroke: var(--amber);
    stroke-width: 1.5;
    stroke-dasharray: 1000;
    stroke-dashoffset: 1000;
    opacity: 0.8;
    transition: stroke-dashoffset 2s ease;
}

.contour-line.animated {
    stroke-dashoffset: 0;
}

.contour-1 { stroke: var(--ember); opacity: 0.4; transition-delay: 0s; }
.contour-2 { stroke: var(--amber); opacity: 0.5; transition-delay: 0.15s; }
.contour-3 { stroke: var(--amber); opacity: 0.6; transition-delay: 0.3s; }
.contour-4 { stroke: var(--coral); opacity: 0.7; transition-delay: 0.45s; }
.contour-5 { stroke: var(--coral); opacity: 0.8; transition-delay: 0.6s; }
.contour-6 { stroke: var(--glow); opacity: 0.9; transition-delay: 0.75s; }
.contour-7 { stroke: var(--glow); opacity: 1; transition-delay: 0.9s; }

.terrain-text {
    font-family: 'IBM Plex Mono', monospace;
    font-weight: 300;
    font-size: clamp(0.75rem, 1.2vw, 0.9rem);
    color: var(--text-muted);
    margin-top: 2rem;
    letter-spacing: 0.04em;
    max-width: 500px;
    margin-left: auto;
    margin-right: auto;
}

/* Section 4: Data Stream */
.data-stream {
    background: var(--ocean-mid);
}

.transmission-log {
    max-width: 480px;
    text-align: left;
}

.transmission {
    opacity: 0;
    transform: translateX(-30px);
    transition: opacity 0.8s ease, transform 0.8s cubic-bezier(0.34, 1.56, 0.64, 1);
    margin-bottom: 1.5rem;
}

.transmission[data-direction="right"] {
    transform: translateX(30px);
}

.transmission.visible {
    opacity: 1;
    transform: translateX(0);
}

.transmission .timestamp {
    font-family: 'IBM Plex Mono', monospace;
    font-weight: 300;
    font-size: 0.75rem;
    color: var(--glow);
    letter-spacing: 0.04em;
    display: block;
    margin-bottom: 0.25rem;
}

.transmission p {
    color: var(--text-primary);
    font-size: clamp(0.9rem, 1.5vw, 1.05rem);
}

.pulse-divider {
    width: 100%;
    height: 1px;
    background: linear-gradient(90deg, transparent, var(--ember), transparent);
    margin: 1.5rem 0;
    opacity: 0.4;
}

/* Section 5: Abyss */
.abyss {
    background: linear-gradient(180deg, var(--ocean-mid) 0%, #050d10 100%);
}

.morph-svg {
    width: min(80vw, 350px);
    height: auto;
    margin-bottom: 2rem;
}

.morph-path {
    fill: none;
    stroke: var(--ember);
    stroke-width: 2;
    filter: drop-shadow(0 0 8px var(--glow));
}

.glow-point {
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background: radial-gradient(circle, var(--glow) 0%, transparent 70%);
    margin: 1rem auto;
    animation: pulse 3s ease-in-out infinite;
    mix-blend-mode: screen;
}

@keyframes pulse {
    0%, 100% { transform: scale(1); opacity: 0.6; }
    50% { transform: scale(2.5); opacity: 1; }
}

.abyss-text {
    font-family: 'Nunito Sans', sans-serif;
    font-weight: 300;
    font-size: clamp(1.1rem, 2vw, 1.4rem);
    letter-spacing: 0.06em;
    color: var(--text-muted);
    margin-top: 1rem;
}

/* Bioluminescent particles */
.bio-particle {
    position: absolute;
    border-radius: 50%;
    background: radial-gradient(circle, var(--glow), transparent 70%);
    mix-blend-mode: screen;
    pointer-events: none;
    animation: bio-pulse 4s ease-in-out infinite;
}

@keyframes bio-pulse {
    0%, 100% { opacity: 0.2; transform: scale(1); }
    50% { opacity: 0.6; transform: scale(1.3); }
}