/* ============================================
   Feynman Flashcards — Landing Page Styles
   ============================================ */

:root {
    --bg: #09090b;
    --bg-subtle: #111114;
    --bg-card: #16161a;
    --bg-card-hover: #1c1c22;
    --border: #27272a;
    --border-subtle: #1e1e22;
    --text: #fafafa;
    --text-muted: #a1a1aa;
    --text-dim: #71717a;
    --accent: #6366f1;
    --accent-light: #818cf8;
    --accent-glow: rgba(99, 102, 241, 0.15);
    --accent-glow-strong: rgba(99, 102, 241, 0.3);
    --gradient-start: #6366f1;
    --gradient-mid: #a78bfa;
    --gradient-end: #c084fc;
    --radius: 16px;
    --radius-sm: 10px;
    --radius-xs: 6px;
    --font: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ---- Reset & Base ---- */

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

html {
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    overflow-x: hidden;
}

a {
    color: inherit;
    text-decoration: none;
}

img {
    display: block;
    max-width: 100%;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

/* ---- Navigation ---- */

.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    padding: 16px 0;
    transition: var(--transition);
    background: transparent;
}

.nav.scrolled {
    background: rgba(9, 9, 11, 0.8);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-subtle);
}

.nav-inner {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 600;
    font-size: 18px;
    letter-spacing: -0.02em;
}

.nav-icon {
    width: 32px;
    height: 32px;
    border-radius: 8px;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 32px;
}

.nav-links a {
    font-size: 14px;
    color: var(--text-muted);
    transition: color var(--transition);
    font-weight: 500;
}

.nav-links a:hover {
    color: var(--text);
}

.nav-cta {
    background: var(--accent);
    color: white !important;
    padding: 8px 20px;
    border-radius: 100px;
    font-weight: 600;
    transition: all var(--transition);
}

.nav-cta:hover {
    background: var(--accent-light);
    transform: translateY(-1px);
}

/* ---- Hero ---- */

.hero {
    position: relative;
    padding: 160px 0 80px;
    text-align: center;
    overflow: hidden;
}

.hero-glow {
    position: absolute;
    top: -200px;
    left: 50%;
    transform: translateX(-50%);
    width: 800px;
    height: 600px;
    background: radial-gradient(ellipse, var(--accent-glow) 0%, transparent 70%);
    pointer-events: none;
}

.hero-badge {
    display: inline-block;
    padding: 6px 16px;
    background: var(--accent-glow);
    border: 1px solid rgba(99, 102, 241, 0.2);
    border-radius: 100px;
    font-size: 13px;
    font-weight: 600;
    color: var(--accent-light);
    margin-bottom: 24px;
    letter-spacing: 0.02em;
}

.hero-title {
    font-size: clamp(48px, 8vw, 80px);
    font-weight: 800;
    line-height: 1.05;
    letter-spacing: -0.04em;
    margin-bottom: 24px;
}

.gradient-text {
    background: linear-gradient(135deg, var(--gradient-start), var(--gradient-mid), var(--gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 18px;
    line-height: 1.7;
    color: var(--text-muted);
    max-width: 600px;
    margin: 0 auto 40px;
}

.hero-actions {
    display: flex;
    gap: 16px;
    justify-content: center;
    flex-wrap: wrap;
    margin-bottom: 80px;
}

/* ---- Buttons ---- */

.btn {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    padding: 14px 28px;
    border-radius: 14px;
    font-size: 15px;
    font-weight: 600;
    transition: all var(--transition);
    cursor: pointer;
    border: none;
    letter-spacing: -0.01em;
}

.btn-primary {
    background: var(--accent);
    color: white;
    box-shadow: 0 0 30px var(--accent-glow-strong);
}

.btn-primary:hover {
    background: var(--accent-light);
    transform: translateY(-2px);
    box-shadow: 0 4px 40px var(--accent-glow-strong);
}

.btn-secondary {
    background: var(--bg-card);
    color: var(--text);
    border: 1px solid var(--border);
}

.btn-secondary:hover {
    background: var(--bg-card-hover);
    border-color: var(--text-dim);
    transform: translateY(-2px);
}

.btn-large {
    padding: 18px 36px;
    font-size: 17px;
    border-radius: 16px;
}

.btn svg {
    flex-shrink: 0;
}

/* ---- Device Mockup ---- */

.hero-device-wrap {
    display: flex;
    justify-content: center;
    perspective: 1200px;
}

.hero-device {
    animation: float 6s ease-in-out infinite;
}

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-12px); }
}

.device-mockup {
    width: 320px;
    background: #1a1a1e;
    border-radius: 40px;
    padding: 12px;
    border: 1px solid #2a2a30;
    box-shadow:
        0 0 0 1px rgba(255,255,255,0.05) inset,
        0 20px 60px rgba(0,0,0,0.5),
        0 0 100px var(--accent-glow);
}

.device-screen {
    background: #0f0f12;
    border-radius: 30px;
    overflow: hidden;
    aspect-ratio: 9/17;
}

.screen-statusbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 14px 24px 8px;
    font-size: 12px;
    font-weight: 600;
    color: var(--text);
}

.screen-notch {
    width: 80px;
    height: 24px;
    background: #000;
    border-radius: 20px;
}

.screen-icons {
    display: flex;
    gap: 2px;
    align-items: flex-end;
}

.bar {
    display: block;
    width: 3px;
    background: var(--text);
    border-radius: 1px;
}

.bar1 { height: 4px; }
.bar2 { height: 7px; }
.bar3 { height: 10px; }

.screen-content {
    padding: 20px 16px;
}

.screen-header {
    font-size: 20px;
    font-weight: 700;
    margin-bottom: 20px;
    letter-spacing: -0.02em;
}

.screen-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 16px;
    margin-bottom: 16px;
}

.screen-label {
    font-size: 11px;
    font-weight: 600;
    color: var(--accent-light);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin-bottom: 8px;
}

.screen-question {
    font-size: 14px;
    font-weight: 500;
    line-height: 1.5;
    color: var(--text);
    margin-bottom: 12px;
}

.screen-source {
    font-size: 11px;
    color: var(--text-dim);
}

.screen-input {
    position: relative;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 12px;
    margin-bottom: 12px;
}

.screen-textarea {
    font-size: 12px;
    line-height: 1.5;
    color: var(--text-muted);
    padding-right: 36px;
    min-height: 60px;
}

.screen-mic {
    position: absolute;
    bottom: 10px;
    right: 10px;
}

.mic-icon {
    width: 28px;
    height: 28px;
    background: var(--accent);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
}

.screen-submit {
    background: var(--accent);
    color: white;
    text-align: center;
    padding: 12px;
    border-radius: 12px;
    font-size: 14px;
    font-weight: 600;
}

/* ---- Hero Trial Note ---- */

.hero-trial-note {
    font-size: 13px;
    color: var(--text-dim);
    margin-top: -60px;
    margin-bottom: 80px;
    text-align: center;
}

/* ---- Proof / Stats ---- */

.proof {
    padding: 60px 0;
    border-top: 1px solid var(--border-subtle);
    border-bottom: 1px solid var(--border-subtle);
}

.proof-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 40px;
    text-align: center;
}

.proof-number {
    font-size: 40px;
    font-weight: 800;
    letter-spacing: -0.04em;
    background: linear-gradient(135deg, var(--text), var(--text-muted));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.proof-label {
    font-size: 14px;
    color: var(--text-dim);
    margin-top: 4px;
}

/* ---- Section Headers ---- */

.section-header {
    text-align: center;
    margin-bottom: 64px;
}

.section-badge {
    display: inline-block;
    padding: 6px 14px;
    background: var(--accent-glow);
    border: 1px solid rgba(99, 102, 241, 0.15);
    border-radius: 100px;
    font-size: 12px;
    font-weight: 600;
    color: var(--accent-light);
    margin-bottom: 20px;
    text-transform: uppercase;
    letter-spacing: 0.06em;
}

.section-title {
    font-size: clamp(32px, 5vw, 48px);
    font-weight: 800;
    line-height: 1.1;
    letter-spacing: -0.03em;
    margin-bottom: 16px;
}

.section-subtitle {
    font-size: 17px;
    color: var(--text-muted);
    max-width: 560px;
    margin: 0 auto;
    line-height: 1.7;
}

/* ---- Problem ---- */

.problem {
    padding: 120px 0;
}

.problem-inner {
    display: grid;
    grid-template-columns: 1.4fr 1fr;
    gap: 60px;
    align-items: center;
}

.problem-text h2 {
    font-size: clamp(28px, 4vw, 40px);
    font-weight: 800;
    line-height: 1.15;
    letter-spacing: -0.03em;
    margin-bottom: 24px;
}

.problem-text p {
    font-size: 16px;
    color: var(--text-muted);
    line-height: 1.8;
    margin-bottom: 16px;
}

.problem-text p:last-child {
    margin-bottom: 0;
}

.problem-text em {
    color: var(--text);
    font-style: italic;
}

.problem-stats {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.problem-stat {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 32px;
    text-align: center;
}

.problem-stat-number {
    font-size: 48px;
    font-weight: 800;
    letter-spacing: -0.04em;
    margin-bottom: 8px;
}

.problem-stat:first-child .problem-stat-number {
    color: #f87171;
}

.problem-stat:last-child .problem-stat-number {
    background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.problem-stat-label {
    font-size: 14px;
    color: var(--text-muted);
    line-height: 1.5;
}

@media (max-width: 768px) {
    .problem-inner {
        grid-template-columns: 1fr;
        gap: 40px;
    }

    .problem-stats {
        flex-direction: row;
    }

    .problem-stat {
        flex: 1;
    }
}

@media (max-width: 480px) {
    .problem-stats {
        flex-direction: column;
    }
}

/* ---- Features ---- */

.features {
    padding: 120px 0;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
}

.feature-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 32px;
    transition: all var(--transition);
}

.feature-card:hover {
    background: var(--bg-card-hover);
    border-color: var(--text-dim);
    transform: translateY(-4px);
    box-shadow: 0 16px 48px rgba(0,0,0,0.3);
}

.feature-large {
    grid-column: 1 / -1;
    display: grid;
    grid-template-columns: auto 1fr;
    grid-template-rows: auto 1fr;
    gap: 0 24px;
    padding: 40px;
    background: linear-gradient(135deg, var(--bg-card), rgba(99,102,241,0.04));
    border-color: rgba(99,102,241,0.15);
}

.feature-large .feature-icon {
    grid-row: 1 / -1;
}

.feature-large h3 {
    font-size: 24px;
}

.feature-large p {
    font-size: 16px;
}

.feature-icon {
    width: 56px;
    height: 56px;
    background: var(--accent-glow);
    border: 1px solid rgba(99, 102, 241, 0.15);
    border-radius: 14px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 20px;
    color: var(--accent-light);
}

.feature-card h3 {
    font-size: 18px;
    font-weight: 700;
    margin-bottom: 10px;
    letter-spacing: -0.02em;
}

.feature-card p {
    font-size: 14px;
    color: var(--text-muted);
    line-height: 1.7;
}

/* ---- How It Works ---- */

.how-it-works {
    padding: 120px 0;
    background: var(--bg-subtle);
    border-top: 1px solid var(--border-subtle);
    border-bottom: 1px solid var(--border-subtle);
}

.steps {
    max-width: 700px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 0;
}

.step {
    display: flex;
    gap: 32px;
    padding: 40px 0;
    border-bottom: 1px solid var(--border-subtle);
    align-items: flex-start;
}

.step:last-child {
    border-bottom: none;
}

.step-number {
    font-size: 48px;
    font-weight: 800;
    letter-spacing: -0.04em;
    color: var(--border);
    line-height: 1;
    flex-shrink: 0;
    width: 80px;
}

.step-content h3 {
    font-size: 20px;
    font-weight: 700;
    margin-bottom: 8px;
    letter-spacing: -0.02em;
}

.step-content p {
    font-size: 15px;
    color: var(--text-muted);
    line-height: 1.7;
}

/* ---- Platforms ---- */

.platforms {
    padding: 120px 0;
}

.platforms-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
}

.platform-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 40px 32px;
    text-align: center;
    transition: all var(--transition);
}

.platform-card:hover {
    background: var(--bg-card-hover);
    border-color: var(--text-dim);
    transform: translateY(-4px);
    box-shadow: 0 16px 48px rgba(0,0,0,0.3);
}

.platform-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto 24px;
    background: var(--accent-glow);
    border: 1px solid rgba(99, 102, 241, 0.15);
    border-radius: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--accent-light);
}

.platform-card h3 {
    font-size: 22px;
    font-weight: 700;
    margin-bottom: 12px;
    letter-spacing: -0.02em;
}

.platform-card p {
    font-size: 14px;
    color: var(--text-muted);
    line-height: 1.7;
    margin-bottom: 20px;
}

.platform-tag {
    display: inline-block;
    padding: 4px 12px;
    background: rgba(255,255,255,0.05);
    border: 1px solid var(--border);
    border-radius: 100px;
    font-size: 12px;
    font-weight: 600;
    color: var(--text-dim);
}

/* ---- Sources ---- */

.sources {
    padding: 120px 0;
    background: var(--bg-subtle);
    border-top: 1px solid var(--border-subtle);
    border-bottom: 1px solid var(--border-subtle);
}

.source-pills {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 12px;
}

.source-pill {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 16px 28px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 100px;
    font-size: 16px;
    font-weight: 600;
    color: var(--text-muted);
    transition: all var(--transition);
}

.source-pill:hover {
    background: var(--bg-card-hover);
    border-color: var(--accent);
    color: var(--text);
    transform: translateY(-2px);
}

.source-pill svg {
    color: var(--accent-light);
}

/* ---- CTA ---- */

.cta {
    padding: 120px 0;
}

.cta-inner {
    position: relative;
    text-align: center;
    padding: 80px 40px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 24px;
    overflow: hidden;
}

.cta-glow {
    position: absolute;
    top: -100px;
    left: 50%;
    transform: translateX(-50%);
    width: 600px;
    height: 400px;
    background: radial-gradient(ellipse, var(--accent-glow) 0%, transparent 70%);
    pointer-events: none;
}

.cta-icon {
    width: 80px;
    height: 80px;
    border-radius: 20px;
    margin: 0 auto 32px;
    position: relative;
    box-shadow: 0 8px 32px rgba(0,0,0,0.3);
}

.cta h2 {
    font-size: clamp(28px, 4vw, 40px);
    font-weight: 800;
    line-height: 1.15;
    letter-spacing: -0.03em;
    margin-bottom: 16px;
    position: relative;
}

.cta p {
    font-size: 17px;
    color: var(--text-muted);
    margin-bottom: 32px;
    position: relative;
}

.cta-actions {
    position: relative;
}

/* ---- Footer ---- */

.footer {
    padding: 40px 0;
    border-top: 1px solid var(--border-subtle);
}

.footer-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 20px;
}

.footer-brand {
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 600;
    font-size: 15px;
}

.footer-icon {
    width: 28px;
    height: 28px;
    border-radius: 7px;
}

.footer-links {
    display: flex;
    gap: 24px;
}

.footer-links a {
    font-size: 13px;
    color: var(--text-dim);
    transition: color var(--transition);
}

.footer-links a:hover {
    color: var(--text);
}

.footer-copy {
    font-size: 13px;
    color: var(--text-dim);
}

/* ---- Animations ---- */

.fade-in {
    opacity: 0;
    transform: translateY(24px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ---- Responsive ---- */

@media (max-width: 900px) {
    .features-grid {
        grid-template-columns: 1fr 1fr;
    }

    .feature-large {
        grid-column: 1 / -1;
        grid-template-columns: 1fr;
    }

    .feature-large .feature-icon {
        grid-row: auto;
    }

    .platforms-grid {
        grid-template-columns: 1fr;
        max-width: 480px;
        margin: 0 auto;
    }

    .proof-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 24px;
    }
}

@media (max-width: 640px) {
    .hero {
        padding: 120px 0 60px;
    }

    .hero-subtitle {
        font-size: 16px;
    }

    .hero-actions {
        flex-direction: column;
        align-items: center;
        margin-bottom: 60px;
    }

    .btn {
        width: 100%;
        max-width: 300px;
        justify-content: center;
    }

    .features-grid {
        grid-template-columns: 1fr;
    }

    .proof-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .nav-links a:not(.nav-cta) {
        display: none;
    }

    .step {
        flex-direction: column;
        gap: 12px;
    }

    .step-number {
        font-size: 36px;
        width: auto;
    }

    .source-pills {
        gap: 8px;
    }

    .source-pill {
        padding: 12px 20px;
        font-size: 14px;
    }

    .footer-inner {
        flex-direction: column;
        text-align: center;
    }

    .cta-inner {
        padding: 60px 24px;
    }

    .device-mockup {
        width: 280px;
    }
}