/* ===========================================================
   Tianqi Personal Site — Design System (refined)
   Single source of truth for colors, spacing, typography,
   breakpoints, and components across all pages.
   =========================================================== */

/* --- Design Tokens --- */
:root {
    /* Color palette */
    --bg-base: #050810;
    --bg-aurora-1: #0a1628;
    --bg-aurora-2: #0d1a2e;
    --bg-aurora-3: #0a1020;
    --bg-surface: rgba(255, 255, 255, 0.04);
    --bg-surface-hover: rgba(255, 255, 255, 0.08);
    --bg-elevated: rgba(13, 22, 40, 0.55);
    --border-subtle: rgba(255, 255, 255, 0.09);
    --border-hover: rgba(88, 166, 255, 0.45);
    --border-glow: rgba(88, 166, 255, 0.18);

    --text-primary: #f0f6fc;
    --text-secondary: #c9d1d9;
    --text-muted: #8b949e;
    --text-dim: rgba(200, 220, 240, 0.5);

    --accent: #58a6ff;
    --accent-hover: #79c0ff;
    --accent-2: #a371f7;
    --accent-glow: rgba(88, 166, 255, 0.5);
    --grad-brand: linear-gradient(135deg, #79c0ff 0%, #58a6ff 45%, #a371f7 100%);

    /* Typography */
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', 'PingFang SC', 'Microsoft YaHei', sans-serif;
    --font-mono: 'SF Mono', 'Fira Code', 'JetBrains Mono', 'Courier New', monospace;

    /* Fluid type scale — clamp() for responsive without media queries */
    --fs-display: clamp(2.2rem, 6.5vw, 3.6rem);
    --fs-h1: clamp(1.8rem, 5vw, 2.8rem);
    --fs-h2: clamp(1.4rem, 4vw, 2.2rem);
    --fs-h3: clamp(1.1rem, 3vw, 1.3rem);
    --fs-body: clamp(0.95rem, 2.5vw, 1.05rem);
    --fs-small: 0.85rem;
    --fs-mono: 0.85rem;

    /* Spacing scale */
    --sp-xs: 0.5rem;
    --sp-sm: 1rem;
    --sp-md: 1.5rem;
    --sp-lg: 2rem;
    --sp-xl: 3rem;
    --sp-2xl: 4rem;

    /* Layout */
    --content-max: 760px;
    --wide-max: 1100px;
    --nav-height: 60px;

    /* Radius */
    --radius: 18px;
    --radius-sm: 10px;
    --radius-pill: 999px;

    /* Transitions */
    --t-fast: 0.18s ease;
    --t-normal: 0.3s cubic-bezier(0.22, 1, 0.36, 1);
    --t-slow: 0.6s cubic-bezier(0.22, 1, 0.36, 1);

    /* Shadows */
    --shadow-card: 0 10px 40px rgba(0, 0, 0, 0.35);
    --shadow-card-hover: 0 20px 60px rgba(0, 0, 0, 0.45);
    --shadow-glow: 0 0 40px rgba(88, 166, 255, 0.18);
}

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

html {
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
}

::selection {
    background: rgba(88, 166, 255, 0.35);
    color: #ffffff;
}

body {
    font-family: var(--font-sans);
    color: var(--text-secondary);
    min-height: 100vh;
    min-height: 100svh;
    overflow-x: hidden;
    position: relative;
    font-size: var(--fs-body);
    line-height: 1.75;
    -webkit-font-smoothing: antialiased;
    text-rendering: optimizeLegibility;
    /* Aurora gradient background — always works, no canvas needed */
    background:
        radial-gradient(ellipse 80% 60% at 20% 0%, rgba(88, 166, 255, 0.09), transparent),
        radial-gradient(ellipse 60% 50% at 80% 20%, rgba(163, 113, 247, 0.08), transparent),
        radial-gradient(ellipse 70% 50% at 50% 100%, rgba(88, 166, 255, 0.06), transparent),
        linear-gradient(180deg, var(--bg-aurora-1) 0%, var(--bg-aurora-3) 50%, var(--bg-base) 100%);
    background-attachment: fixed;
}

/* Pretty scrollbar (WebKit) */
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb {
    background: rgba(88, 166, 255, 0.25);
    border-radius: var(--radius-pill);
    border: 2px solid transparent;
    background-clip: content-box;
}
::-webkit-scrollbar-thumb:hover { background: rgba(88, 166, 255, 0.45); background-clip: content-box; }

/* Accessible focus */
:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 3px;
    border-radius: 4px;
}

/* --- Canvas Background --- */
#glass-canvas {
    position: fixed;
    inset: 0;
    z-index: 0;
    pointer-events: none;
}

/* --- Scroll progress bar --- */
.progress-bar {
    position: fixed;
    top: 0;
    left: 0;
    height: 3px;
    width: 0%;
    background: var(--grad-brand);
    box-shadow: 0 0 12px rgba(88, 166, 255, 0.6);
    z-index: 70;
    border-radius: 0 3px 3px 0;
    transition: width 0.06s linear;
}

/* --- Clock --- */
.clock {
    position: fixed;
    top: 0;
    right: 20px;
    height: var(--nav-height);
    display: flex;
    align-items: center;
    color: var(--text-dim);
    font-size: var(--fs-mono);
    font-family: var(--font-mono);
    letter-spacing: 0.04em;
    z-index: 60;
    pointer-events: none;
}

/* --- Navigation --- */
nav {
    position: fixed;
    top: 0; left: 0; right: 0;
    z-index: 50;
    background: rgba(5, 8, 16, 0.55);
    backdrop-filter: blur(16px) saturate(150%);
    -webkit-backdrop-filter: blur(16px) saturate(150%);
    border-bottom: 1px solid var(--border-subtle);
    transition: background var(--t-normal), box-shadow var(--t-normal);
}
nav.scrolled {
    background: rgba(5, 8, 16, 0.82);
    box-shadow: 0 6px 24px rgba(0, 0, 0, 0.35);
}

.nav-inner {
    max-width: var(--wide-max);
    margin: 0 auto;
    padding: 0 var(--sp-md);
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: var(--nav-height);
}

.brand {
    font-size: 1.2em;
    font-weight: 700;
    color: var(--accent);
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: 10px;
    letter-spacing: 0.01em;
}

.nav-links {
    display: flex;
    gap: var(--sp-sm);
    align-items: center;
}

.nav-links a {
    position: relative;
    color: var(--text-muted);
    text-decoration: none;
    font-size: var(--fs-body);
    padding: 6px 12px;
    border-radius: var(--radius-sm);
    transition: color var(--t-fast), background var(--t-fast);
    white-space: nowrap;
}
.nav-links a:hover {
    color: var(--text-primary);
    background: rgba(255, 255, 255, 0.05);
}
.nav-links a.active {
    color: var(--accent-hover);
}
.nav-links a.active::after {
    content: "";
    position: absolute;
    left: 12px;
    right: 12px;
    bottom: 2px;
    height: 2px;
    border-radius: 2px;
    background: var(--grad-brand);
}

/* Mobile hamburger */
.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
    z-index: 60;
}
.nav-toggle span {
    width: 24px;
    height: 2px;
    background: var(--text-secondary);
    border-radius: 2px;
    transition: var(--t-normal);
}
.nav-toggle.open span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
.nav-toggle.open span:nth-child(2) { opacity: 0; }
.nav-toggle.open span:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

/* --- Main / Layout --- */
main { position: relative; z-index: 1; }

/* Hero sections — full viewport */
.section {
    min-height: 100vh;
    min-height: 100svh; /* mobile-safe */
    display: flex;
    align-items: center;
    justify-content: center;
    padding: calc(var(--nav-height) + var(--sp-xl)) var(--sp-md) var(--sp-xl);
}

/* Content page — scrollable */
.page {
    max-width: var(--content-max);
    margin: 0 auto;
    padding: calc(var(--nav-height) + var(--sp-2xl)) var(--sp-md) var(--sp-xl);
    position: relative;
    z-index: 1;
}
.page-wide { max-width: var(--wide-max); }

/* --- Glass card (hero blocks) --- */
.glass-card {
    max-width: var(--content-max);
    width: 100%;
    text-align: center;
    padding: clamp(2rem, 6vw, 3.5rem) clamp(1.25rem, 5vw, 2.5rem);
    background: var(--bg-elevated);
    backdrop-filter: blur(18px) saturate(140%);
    -webkit-backdrop-filter: blur(18px) saturate(140%);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius);
    box-shadow: var(--shadow-card),
                inset 0 1px 0 rgba(255, 255, 255, 0.06);
    transition: transform var(--t-slow), box-shadow var(--t-slow), border-color var(--t-normal);
}
.glass-card:hover {
    transform: translateY(-4px);
    border-color: var(--border-glow);
    box-shadow: var(--shadow-card-hover), var(--shadow-glow),
                inset 0 1px 0 rgba(255, 255, 255, 0.08);
}

/* --- Fade-in on scroll --- */
.hero-content, .section-content, .page > * {
    opacity: 0;
    transform: translateY(28px);
    transition: opacity 0.7s ease, transform 0.7s cubic-bezier(0.22, 1, 0.36, 1);
}
.section.visible .hero-content,
.section.visible .section-content,
.page.visible > * {
    opacity: 1;
    transform: translateY(0);
}

/* --- Typography --- */
h1 {
    font-size: var(--fs-display);
    color: var(--text-primary);
    margin-bottom: var(--sp-sm);
    letter-spacing: -0.03em;
    font-weight: 800;
    line-height: 1.15;
}
h2 {
    font-size: var(--fs-h2);
    color: var(--text-primary);
    margin-bottom: var(--sp-md);
    letter-spacing: -0.02em;
    font-weight: 700;
}
h3 {
    font-size: var(--fs-h3);
    color: var(--text-primary);
    margin-bottom: var(--sp-xs);
    font-weight: 600;
}

/* Gradient headline for hero */
.grad-text {
    background: var(--grad-brand);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    color: transparent;
}

.subtitle {
    font-size: clamp(1.05rem, 3vw, 1.3rem);
    color: var(--accent);
    margin-bottom: var(--sp-md);
    font-weight: 500;
    letter-spacing: 0.01em;
}

p {
    color: var(--text-muted);
    line-height: 1.85;
    margin-bottom: var(--sp-sm);
}

/* --- Logo --- */
.logo-wrap { display: inline-block; margin-bottom: var(--sp-lg); }

.hero-logo {
    width: clamp(100px, 25vw, 160px);
    height: clamp(100px, 25vw, 160px);
    object-fit: contain;
    filter: drop-shadow(0 0 32px var(--accent-glow));
    transition: transform var(--t-slow), filter 0.5s;
}
.logo-wrap:hover .hero-logo {
    transform: scale(1.12) rotate(4deg);
    filter: drop-shadow(0 0 54px rgba(88, 166, 255, 0.95));
}

.end-logo {
    width: clamp(60px, 15vw, 90px);
    height: clamp(60px, 15vw, 90px);
    object-fit: contain;
    filter: drop-shadow(0 0 20px rgba(88, 166, 255, 0.4));
    margin-bottom: var(--sp-sm);
    transition: transform 0.5s;
}
.end-logo:hover { transform: scale(1.1) rotate(15deg); }

.logo {
    height: 32px;
    width: 32px;
    object-fit: contain;
    transition: transform 0.5s;
}
.brand:hover .logo { transform: scale(1.18) rotate(8deg); }

/* --- Scroll hint --- */
.scroll-hint {
    position: fixed;
    bottom: var(--sp-lg);
    left: 50%;
    text-align: center;
    color: var(--text-dim);
    font-size: var(--fs-small);
    animation: bounce 2s ease-in-out infinite;
    z-index: 10;
    pointer-events: none;
    opacity: 0.75;
    transition: opacity 0.8s ease-out;
}
.scroll-hint .arrow { font-size: 1.4em; margin-top: 6px; }
.scroll-hint.hidden { opacity: 0; transition: opacity 1.2s ease-out; }
@keyframes bounce {
    0%, 100% { transform: translateX(-50%) translateY(0); }
    50% { transform: translateX(-50%) translateY(-8px); }
}

/* --- Cards --- */
.cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(min(260px, 100%), 1fr));
    gap: var(--sp-md);
    margin-top: var(--sp-lg);
}

.card {
    display: block;
    padding: var(--sp-lg);
    text-align: center;
    text-decoration: none;
    color: var(--text-secondary);
    background: var(--bg-surface);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-sm);
    box-shadow: var(--shadow-card);
    transition: transform var(--t-normal), border-color var(--t-normal),
                background var(--t-normal), box-shadow var(--t-normal);
}
.card:hover {
    transform: translateY(-6px);
    border-color: var(--border-hover);
    background: var(--bg-surface-hover);
    box-shadow: var(--shadow-card-hover), var(--shadow-glow);
}

.card-icon { font-size: 2.2em; margin-bottom: var(--sp-sm); }
.card h3 { font-size: var(--fs-h3); margin-bottom: var(--sp-xs); }
.card p { font-size: var(--fs-small); margin-bottom: var(--sp-sm); }
.card-link {
    color: var(--accent);
    font-size: var(--fs-mono);
    font-family: var(--font-mono);
    display: inline-block;
    transition: transform var(--t-fast);
}
.card:hover .card-link { transform: translateX(5px); }

/* --- Buttons --- */
.btn {
    display: inline-block;
    padding: 11px 26px;
    color: var(--accent);
    text-decoration: none;
    font-weight: 600;
    font-size: var(--fs-body);
    border: 1px solid var(--border-hover);
    border-radius: var(--radius-sm);
    background: rgba(88, 166, 255, 0.06);
    transition: transform var(--t-fast), color var(--t-fast),
                border-color var(--t-fast), background var(--t-fast),
                box-shadow var(--t-fast);
    margin-top: var(--sp-md);
}
.btn:hover {
    color: #ffffff;
    background: var(--grad-brand);
    border-color: transparent;
    transform: translateY(-2px);
    box-shadow: 0 8px 24px rgba(88, 166, 255, 0.35);
}
.btn:active { transform: translateY(0); }

/* --- Back to top --- */
.to-top {
    position: fixed;
    right: 22px;
    bottom: 22px;
    width: 46px;
    height: 46px;
    border-radius: 50%;
    border: 1px solid var(--border-hover);
    background: rgba(13, 22, 40, 0.7);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    color: var(--accent);
    font-size: 1.2rem;
    line-height: 1;
    cursor: pointer;
    z-index: 65;
    opacity: 0;
    transform: translateY(16px);
    pointer-events: none;
    transition: opacity var(--t-normal), transform var(--t-normal),
                background var(--t-fast), box-shadow var(--t-fast);
}
.to-top.show {
    opacity: 1;
    transform: translateY(0);
    pointer-events: auto;
}
.to-top:hover {
    background: var(--grad-brand);
    color: #fff;
    box-shadow: 0 8px 24px rgba(88, 166, 255, 0.4);
}

/* --- Service blocks (shared component) --- */
.service-block {
    margin-bottom: var(--sp-xl);
    padding: var(--sp-lg);
    background: var(--bg-surface);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius);
    text-align: left;
    transition: border-color var(--t-normal), background var(--t-normal), transform var(--t-normal);
}
.service-block:hover {
    border-color: var(--border-glow);
    background: var(--bg-surface-hover);
    transform: translateY(-3px);
}

.service-head {
    display: flex;
    align-items: center;
    gap: var(--sp-sm);
    margin-bottom: var(--sp-sm);
}

.service-icon { font-size: 1.9em; line-height: 1; }

.service-block h2 {
    font-size: clamp(1.2rem, 3.5vw, 1.5rem);
    margin: 0;
}

.service-points {
    list-style: none;
    padding: 0;
    margin: 0;
}
.service-points li {
    color: var(--text-secondary);
    line-height: 1.8;
    font-size: var(--fs-body);
    padding: var(--sp-xs) 0 var(--sp-xs) 22px;
    position: relative;
}
.service-points li::before {
    content: "▸";
    color: var(--accent);
    position: absolute;
    left: 0;
    top: var(--sp-xs);
    font-size: 0.85em;
}

/* --- Page header (shared) --- */
.page-title {
    font-size: var(--fs-h1);
    color: var(--text-primary);
    text-align: center;
    margin-bottom: var(--sp-sm);
    font-weight: 800;
    letter-spacing: -0.02em;
}

.page-subtitle {
    text-align: center;
    color: var(--text-muted);
    margin-bottom: var(--sp-2xl);
}

.page-footer-hint {
    text-align: center;
    color: rgba(139, 148, 158, 0.7);
    font-size: var(--fs-small);
    margin-top: var(--sp-xl);
    padding-top: var(--sp-lg);
    border-top: 1px solid var(--border-subtle);
}

/* --- About page --- */
.about-grid {
    display: grid;
    gap: var(--sp-lg);
    margin-top: var(--sp-lg);
}
.about-card {
    padding: var(--sp-lg);
    background: var(--bg-surface);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius);
    transition: border-color var(--t-normal), background var(--t-normal), transform var(--t-normal);
}
.about-card:hover {
    border-color: var(--border-glow);
    background: var(--bg-surface-hover);
    transform: translateY(-3px);
}
.about-card h3 {
    margin-bottom: var(--sp-sm);
    color: var(--accent);
}
.about-card .icon { font-size: 1.8em; margin-bottom: var(--sp-xs); display: block; }
.tag-list {
    display: flex;
    flex-wrap: wrap;
    gap: var(--sp-xs);
    margin-top: var(--sp-sm);
}
.tag {
    padding: 4px 12px;
    background: rgba(88, 166, 255, 0.1);
    border: 1px solid rgba(88, 166, 255, 0.22);
    border-radius: var(--radius-pill);
    color: var(--accent);
    font-size: 0.8rem;
    font-family: var(--font-mono);
    transition: background var(--t-fast), border-color var(--t-fast), transform var(--t-fast);
}
.tag:hover {
    background: rgba(88, 166, 255, 0.18);
    border-color: rgba(88, 166, 255, 0.4);
    transform: translateY(-2px);
}

/* --- Footer --- */
footer {
    text-align: center;
    padding: var(--sp-lg) var(--sp-md);
    color: var(--text-dim);
    font-size: var(--fs-small);
    position: relative;
    z-index: 1;
}
footer .beian {
    margin-top: var(--sp-xs);
    font-size: var(--fs-small);
}
footer .beian a {
    color: var(--text-dim);
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    transition: color var(--t-normal);
}
footer .beian a:hover { color: var(--text-secondary); }
footer .beian-icon {
    width: 18px;
    height: 20px;
    vertical-align: middle;
}

/* --- Mobile Navigation --- */
@media (max-width: 640px) {
    .nav-toggle { display: flex; }

    .nav-links {
        position: fixed;
        top: 0;
        right: 0;
        width: 70%;
        max-width: 280px;
        height: 100vh;
        height: 100svh;
        flex-direction: column;
        justify-content: center;
        gap: var(--sp-xl);
        background: rgba(5, 8, 16, 0.96);
        backdrop-filter: blur(20px);
        -webkit-backdrop-filter: blur(20px);
        border-left: 1px solid var(--border-subtle);
        transform: translateX(100%);
        transition: transform var(--t-normal);
        z-index: 55;
    }
    .nav-links.open { transform: translateX(0); }
    .nav-links a { font-size: 1.2em; }

    .clock { font-size: 0.75rem; right: 62px; }

    .section { padding: calc(var(--nav-height) + var(--sp-lg)) var(--sp-sm) var(--sp-lg); }
    .page { padding: calc(var(--nav-height) + var(--sp-xl)) var(--sp-sm) var(--sp-lg); }

    .service-block { padding: var(--sp-md); }
    .glass-card { padding: 2rem 1.25rem; }
    .to-top { right: 16px; bottom: 16px; width: 42px; height: 42px; }
}

/* --- Reduced motion --- */
@media (prefers-reduced-motion: reduce) {
    html { scroll-behavior: auto; }
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        transition-duration: 0.01ms !important;
    }
    .scroll-hint { display: none; }
}

/* --- Print --- */
@media print {
    #glass-canvas, .clock, .scroll-hint, nav, .to-top, .progress-bar { display: none; }
    body { background: white; color: black; }
}