/* ===== Reset & base ===== */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", "Segoe UI", "Helvetica Neue", Arial, sans-serif;
    font-size: 16px;
    line-height: 1.7;
    color: var(--text);
    background: var(--bg);
    -webkit-font-smoothing: antialiased;
    transition: background-color .3s ease, color .3s ease;
}

/* ===== Theme tokens ===== */
:root {
    --bg: #f4f7fb;
    --bg-alt: #ffffff;
    --surface: #ffffff;
    --text: #1a2733;
    --text-soft: #4a5a6a;
    --text-mute: #7a8896;
    --accent: #1f6feb;
    --accent-soft: #4a9bff;
    --deep: #0a3d62;
    --border: #e1e8ef;
    --shadow: 0 6px 24px rgba(15, 40, 80, .06);
    --radius: 14px;
}
[data-theme="dark"] {
    --bg: #0d1620;
    --bg-alt: #0a1320;
    --surface: #142133;
    --text: #e3edf7;
    --text-soft: #b5c3d4;
    --text-mute: #8294a8;
    --accent: #4a9bff;
    --accent-soft: #7cb6ff;
    --deep: #6cb2ff;
    --border: #1f3145;
    --shadow: 0 6px 24px rgba(0, 0, 0, .35);
}

/* ===== Layout ===== */
.container { width: min(1080px, 92vw); margin: 0 auto; }

/* ===== Nav ===== */
.nav {
    position: sticky;
    top: 0;
    z-index: 50;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    backdrop-filter: saturate(180%) blur(12px);
}
.nav-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 64px;
}
.logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text);
    text-decoration: none;
    letter-spacing: .3px;
}
.logo .dot { color: var(--accent); }
.nav-links { display: flex; gap: 1.6rem; }
.nav-links a {
    color: var(--text-soft);
    text-decoration: none;
    font-size: .95rem;
    transition: color .2s;
}
.nav-links a:hover { color: var(--accent); }
.theme-toggle {
    background: none;
    border: 1px solid var(--border);
    border-radius: 999px;
    width: 38px; height: 38px;
    cursor: pointer;
    font-size: 1rem;
    color: var(--text);
    transition: background-color .2s, transform .2s;
}
.theme-toggle:hover { background: var(--bg); transform: translateY(-1px); }

/* ===== Hero ===== */
.hero {
    position: relative;
    padding: 7rem 0 9rem;
    background: linear-gradient(180deg, var(--bg) 0%, var(--bg-alt) 100%);
    overflow: hidden;
}
.hero-inner { max-width: 760px; }
.hero-badge {
    display: inline-block;
    padding: .35rem .9rem;
    border-radius: 999px;
    background: var(--surface);
    border: 1px solid var(--border);
    color: var(--text-soft);
    font-size: .85rem;
    margin-bottom: 1.4rem;
}
.hero-title {
    font-size: clamp(2rem, 5vw, 3rem);
    line-height: 1.25;
    margin: 0 0 1.2rem;
    font-weight: 800;
    letter-spacing: -.5px;
}
.hero-title .accent {
    color: var(--accent);
    background: linear-gradient(120deg, var(--accent), var(--deep));
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}
.hero-sub {
    font-size: 1.1rem;
    color: var(--text-soft);
    margin: 0 0 2rem;
}
.hero-cta { display: flex; gap: 1rem; flex-wrap: wrap; }
.btn {
    display: inline-block;
    padding: .75rem 1.5rem;
    border-radius: 10px;
    text-decoration: none;
    font-weight: 600;
    font-size: .95rem;
    transition: transform .15s, box-shadow .2s, background-color .2s;
}
.btn-primary {
    background: var(--accent);
    color: #fff;
    box-shadow: 0 6px 18px rgba(31, 111, 235, .25);
}
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 10px 22px rgba(31, 111, 235, .35); }
.btn-ghost {
    background: transparent;
    color: var(--text);
    border: 1px solid var(--border);
}
.btn-ghost:hover { background: var(--surface); }

/* ===== Waves ===== */
.waves {
    position: absolute;
    left: 0; right: 0; bottom: -1px;
    line-height: 0;
}
.waves svg {
    width: 100%;
    height: 90px;
    display: block;
}
.waves path { fill: var(--bg-alt); }

/* ===== Sections ===== */
.section { padding: 5.5rem 0; }
.section-alt { background: var(--bg-alt); }
.section-title {
    font-size: 1.7rem;
    margin: 0 0 .5rem;
    font-weight: 700;
    letter-spacing: -.3px;
}
.section-desc {
    color: var(--text-mute);
    margin: 0 0 2.5rem;
}

/* ===== About ===== */
.about-grid {
    display: grid;
    grid-template-columns: 1.4fr 1fr;
    gap: 3rem;
    align-items: start;
}
.about-text p { color: var(--text-soft); margin: 0 0 1rem; }
.about-text code {
    background: var(--surface);
    border: 1px solid var(--border);
    padding: .1rem .4rem;
    border-radius: 5px;
    font-size: .9em;
    color: var(--accent);
}
.about-tags {
    list-style: none;
    padding: 0;
    margin: 1.5rem 0 0;
    display: flex;
    flex-wrap: wrap;
    gap: .6rem;
}
.about-tags li {
    background: var(--surface);
    border: 1px solid var(--border);
    padding: .4rem .9rem;
    border-radius: 999px;
    font-size: .9rem;
    color: var(--text-soft);
}
.about-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
}
.card-row {
    display: flex;
    justify-content: space-between;
    padding: .55rem 0;
    border-bottom: 1px dashed var(--border);
    font-size: .92rem;
}
.card-row:last-child { border-bottom: none; }
.card-row span { color: var(--text-mute); }
.card-row b { color: var(--text); font-weight: 600; }

/* ===== Logbook ===== */
.logbook {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 1.5rem;
}
.log-item {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.6rem;
    box-shadow: var(--shadow);
    transition: transform .2s, box-shadow .2s;
}
.log-item:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 30px rgba(15, 40, 80, .12);
}
.log-date {
    color: var(--accent);
    font-weight: 600;
    font-size: .85rem;
    letter-spacing: .5px;
    margin-bottom: .5rem;
}
.log-item h3 { margin: 0 0 .6rem; font-size: 1.1rem; }
.log-item p { color: var(--text-soft); margin: 0 0 1rem; font-size: .95rem; }
.log-more { color: var(--accent); text-decoration: none; font-size: .9rem; font-weight: 600; }
.log-more:hover { color: var(--deep); }

/* ===== Projects ===== */
.projects {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 1.5rem;
}
.project-card {
    display: block;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.8rem;
    text-decoration: none;
    color: var(--text);
    box-shadow: var(--shadow);
    transition: transform .2s, border-color .2s;
}
.project-card:hover { transform: translateY(-4px); border-color: var(--accent); }
.project-emoji {
    font-size: 2.2rem;
    margin-bottom: .8rem;
}
.project-card h3 { margin: 0 0 .5rem; font-size: 1.1rem; }
.project-card p { color: var(--text-soft); margin: 0 0 1rem; font-size: .92rem; }
.project-tag {
    display: inline-block;
    background: var(--bg);
    color: var(--accent);
    font-size: .8rem;
    padding: .2rem .7rem;
    border-radius: 999px;
    border: 1px solid var(--border);
}

/* ===== Contact ===== */
.contact-inner { text-align: center; max-width: 640px; }
.contact-lead {
    color: var(--text-soft);
    margin: 1rem 0 2.5rem;
    font-size: 1.05rem;
}
.contact-channels {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    max-width: 420px;
    margin: 0 auto;
    text-align: left;
}
.channel {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem 1.2rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    text-decoration: none;
    color: var(--text);
    transition: border-color .2s, transform .2s;
}
.channel:hover { border-color: var(--accent); transform: translateX(4px); }
.channel-emoji { font-size: 1.4rem; }
.channel b { display: block; font-size: .95rem; }
.channel em {
    font-style: normal;
    color: var(--text-mute);
    font-size: .88rem;
}

/* ===== Footer ===== */
.footer {
    background: var(--surface);
    border-top: 1px solid var(--border);
    padding: 3rem 0 2rem;
    color: var(--text-soft);
}
.footer-inner {
    display: grid;
    grid-template-columns: 1.4fr 1fr 1.4fr;
    gap: 2rem;
    align-items: start;
}
.footer-logo {
    font-weight: 700;
    color: var(--text);
    font-size: 1.1rem;
}
.footer-tag { margin: .5rem 0 0; font-size: .88rem; color: var(--text-mute); }
.footer-links {
    display: flex;
    flex-direction: column;
    gap: .5rem;
}
.footer-links a {
    color: var(--text-soft);
    text-decoration: none;
    font-size: .92rem;
}
.footer-links a:hover { color: var(--accent); }
.footer-meta { text-align: right; font-size: .88rem; }
.footer-meta p { margin: .25rem 0; }
.footer-meta .beian a {
    color: var(--text-mute);
    text-decoration: none;
    transition: color .2s;
}
.footer-meta .beian a:hover { color: var(--accent); text-decoration: underline; }

/* ===== Responsive ===== */
@media (max-width: 820px) {
    .nav-links { display: none; }
    .about-grid { grid-template-columns: 1fr; gap: 2rem; }
    .footer-inner { grid-template-columns: 1fr; text-align: left; }
    .footer-meta { text-align: left; }
    .hero { padding: 4rem 0 6rem; }
    .section { padding: 4rem 0; }
}