/* ─────────────────────────────────────────────────────────────
   liucao.me — shared design system
   Dark theme, emerald accent, modern type scale
   ───────────────────────────────────────────────────────────── */

:root {
    --bg:        #0b0f14;
    --bg-soft:   #11171f;
    --surface:   #151c26;
    --surface-2: #1b2430;
    --border:    #26313f;
    --border-hi: #34455a;
    --text:      #e8edf2;
    --text-dim:  #9aa7b4;
    --text-mute: #64717f;
    --accent:    #00e5a0;
    --accent-dim:#0bbd87;
    --accent-glow: rgba(0, 229, 160, 0.15);
    --danger:    #ef4444;
    --radius:    14px;
    --radius-sm: 8px;
    --maxw:      1040px;
    --shadow:    0 10px 40px rgba(0,0,0,0.35);
    --font: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --mono: 'SF Mono', 'JetBrains Mono', 'Fira Code', ui-monospace, Menlo, monospace;
}

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

html { scroll-behavior: smooth; }

body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    background-image:
        radial-gradient(900px 500px at 15% -10%, rgba(0,229,160,0.08), transparent 60%),
        radial-gradient(700px 500px at 100% 0%, rgba(56,132,255,0.06), transparent 55%);
    background-attachment: fixed;
}

a { color: var(--accent); text-decoration: none; }

/* ── Top nav ── */
.nav {
    position: sticky;
    top: 0;
    z-index: 50;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem 1.5rem;
    max-width: var(--maxw);
    margin: 0 auto;
    backdrop-filter: blur(8px);
}
.nav .brand {
    font-weight: 700;
    font-size: 1.05rem;
    letter-spacing: -0.01em;
    color: var(--text);
}
.nav .brand span { color: var(--accent); }
.nav .links { display: flex; gap: 0.4rem; align-items: center; }
.nav .links a {
    color: var(--text-dim);
    font-size: 0.9rem;
    padding: 0.45rem 0.85rem;
    border-radius: var(--radius-sm);
    transition: color 0.18s, background 0.18s;
}
.nav .links a:hover { color: var(--text); background: var(--surface); }
.nav .links a.cta {
    color: var(--accent);
    border: 1px solid var(--border);
}
.nav .links a.cta:hover { border-color: var(--accent); background: var(--accent-glow); }

/* ── Layout helpers ── */
.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 1.5rem; }
.section { padding: 3rem 0; }

.back {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    color: var(--text-mute);
    font-size: 0.9rem;
    transition: color 0.18s;
}
.back:hover { color: var(--accent); }

/* ── Hero ── */
.hero { text-align: center; padding: 5rem 1.5rem 3.5rem; }
.hero .eyebrow {
    display: inline-block;
    font-family: var(--mono);
    font-size: 0.78rem;
    color: var(--accent);
    background: var(--accent-glow);
    border: 1px solid var(--border);
    padding: 0.35rem 0.85rem;
    border-radius: 999px;
    margin-bottom: 1.4rem;
    letter-spacing: 0.02em;
}
.hero h1 {
    font-size: clamp(2.4rem, 6vw, 3.8rem);
    font-weight: 700;
    letter-spacing: -0.03em;
    line-height: 1.05;
    margin-bottom: 1rem;
}
.hero h1 .grad {
    background: linear-gradient(120deg, var(--accent), #5eead4 55%, #38bdf8);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}
.hero p.sub {
    color: var(--text-dim);
    font-size: clamp(1rem, 2.2vw, 1.2rem);
    max-width: 560px;
    margin: 0 auto 2.2rem;
}
.hero .actions { display: flex; gap: 0.9rem; justify-content: center; flex-wrap: wrap; }

.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.6rem;
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.15s, background 0.18s, border-color 0.18s, opacity 0.18s;
    border: 1px solid transparent;
}
.btn-primary { background: var(--accent); color: #04120d; }
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 8px 24px var(--accent-glow); }
.btn-ghost { border-color: var(--border); color: var(--text); }
.btn-ghost:hover { border-color: var(--accent); color: var(--accent); }

/* ── Card grid ── */
.grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.25rem;
}
.card {
    position: relative;
    background: linear-gradient(180deg, var(--surface), var(--bg-soft));
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.5rem;
    color: inherit;
    display: block;
    overflow: hidden;
    transition: border-color 0.2s, transform 0.15s, box-shadow 0.2s;
}
.card::before {
    content: "";
    position: absolute;
    inset: 0 0 auto 0;
    height: 2px;
    background: linear-gradient(90deg, transparent, var(--accent), transparent);
    opacity: 0;
    transition: opacity 0.25s;
}
.card:hover { border-color: var(--accent-dim); transform: translateY(-3px); box-shadow: var(--shadow); }
.card:hover::before { opacity: 1; }
.card h3 { font-size: 1.1rem; color: var(--accent); margin-bottom: 0.5rem; letter-spacing: -0.01em; }
.card .meta { color: var(--text-mute); font-size: 0.8rem; margin-bottom: 0.5rem; font-family: var(--mono); }
.card p { color: var(--text-dim); font-size: 0.88rem; line-height: 1.55; }
.card .tag {
    display: inline-block;
    margin-top: 0.9rem;
    padding: 0.22rem 0.65rem;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 999px;
    font-size: 0.72rem;
    color: var(--text-mute);
    font-family: var(--mono);
}

/* ── Section heading ── */
.section-head { text-align: center; margin-bottom: 2.5rem; }
.section-head h1 { font-size: 2.2rem; font-weight: 700; letter-spacing: -0.02em; margin-bottom: 0.4rem; }
.section-head h1 span { color: var(--accent); }
.section-head p { color: var(--text-dim); }

/* ── Login ── */
.login-container {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    padding: 1.5rem;
}
.login-box {
    background: linear-gradient(180deg, var(--surface), var(--bg-soft));
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 2.6rem;
    width: 100%;
    max-width: 380px;
    box-shadow: var(--shadow);
}
.login-box .logo { text-align: center; font-weight: 700; font-size: 1.5rem; margin-bottom: 0.3rem; letter-spacing: -0.02em; }
.login-box .logo span { color: var(--accent); }
.login-box .subtitle { text-align: center; color: var(--text-mute); font-size: 0.85rem; margin-bottom: 1.9rem; }
.form-group { margin-bottom: 1rem; }
.form-group label { display: block; font-size: 0.8rem; color: var(--text-dim); margin-bottom: 0.35rem; }
.form-group input {
    width: 100%;
    padding: 0.75rem 0.9rem;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text);
    font-size: 0.92rem;
    outline: none;
    transition: border-color 0.18s, box-shadow 0.18s;
}
.form-group input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-glow); }
.password-wrapper { position: relative; }
.password-wrapper input { padding-right: 3.6rem; }
.toggle-pw {
    position: absolute; right: 0.5rem; top: 50%; transform: translateY(-50%);
    background: none; border: none; color: var(--text-mute);
    font-size: 0.75rem; cursor: pointer; padding: 0.3rem 0.5rem;
}
.toggle-pw:hover { color: var(--accent); }
.login-btn {
    width: 100%; padding: 0.8rem; background: var(--accent); color: #04120d;
    border: none; border-radius: var(--radius-sm); font-size: 0.92rem;
    font-weight: 600; cursor: pointer; margin-top: 0.6rem; transition: opacity 0.18s, transform 0.15s;
}
.login-btn:hover { opacity: 0.92; transform: translateY(-1px); }
.error-msg { color: var(--danger); font-size: 0.82rem; text-align: center; margin-top: 0.9rem; }

/* ── Footer ── */
.footer {
    border-top: 1px solid var(--border);
    margin-top: 4rem;
    padding: 2rem 1.5rem;
    text-align: center;
    color: var(--text-mute);
    font-size: 0.85rem;
}
.footer a { color: var(--text-dim); }
.footer a:hover { color: var(--accent); }

/* ── Responsive ── */
@media (max-width: 600px) {
    .nav { padding: 0.85rem 1rem; }
    .nav .links a { padding: 0.4rem 0.6rem; font-size: 0.85rem; }
    .hero { padding-top: 3.5rem; }
}

/* ── Minimal homepage ── */
.home {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 2rem;
}
.home h1 {
    font-size: clamp(2.5rem, 8vw, 4rem);
    font-weight: 700;
    letter-spacing: -0.03em;
}
.home h1 span { color: var(--accent); }
.home .tagline {
    color: var(--text-dim);
    font-size: 1.05rem;
    margin: 0.6rem 0 2rem;
}
.home-links { display: flex; gap: 1.5rem; }
.home-links a {
    color: var(--text-dim);
    font-size: 0.95rem;
    transition: color 0.18s;
}
.home-links a:hover { color: var(--accent); }