:root {
    --ink: #10120f;
    --paper: #f4f1e8;
    --accent: #20d4c5;
    --muted: #87918e;
    --line: rgba(255, 255, 255, 0.16);
    --display: "Arial Black", "PingFang SC", "Microsoft YaHei", sans-serif;
    --body: "Inter", "PingFang SC", "Microsoft YaHei", sans-serif;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body { min-width: 320px; background: var(--ink); color: var(--paper); font-family: var(--body); line-height: 1.65; overflow-x: hidden; }
a { color: inherit; }

.product-header {
    position: fixed; inset: 0 0 auto; z-index: 100;
    display: grid; grid-template-columns: 1fr auto; align-items: center;
    min-height: 76px; padding: 0 4vw; border-bottom: 1px solid var(--line);
    background: color-mix(in srgb, var(--ink) 88%, transparent); backdrop-filter: blur(18px);
}
.home-link { justify-self: start; text-decoration: none; font-size: 0.78rem; font-weight: 800; letter-spacing: 0.18em; text-transform: uppercase; }
.header-mark { justify-self: end; color: var(--muted); font-size: 0.72rem; letter-spacing: 0.14em; }

.product-hero { position: relative; min-height: 100svh; padding: 150px 8vw 80px; display: grid; align-items: center; isolation: isolate; overflow: hidden; }
.hero-copy { position: relative; z-index: 2; max-width: 1100px; }
.eyebrow { margin-bottom: 1.5rem; color: var(--accent); font-size: 0.78rem; font-weight: 900; letter-spacing: 0.28em; text-transform: uppercase; }
.brand-title { font-family: var(--display); font-size: clamp(5rem, 18vw, 14rem); line-height: 0.86; letter-spacing: -0.08em; }
.brand-title span { display: block; margin-top: 1.5rem; font-family: var(--body); font-size: clamp(1rem, 2vw, 1.45rem); font-weight: 500; line-height: 1.5; letter-spacing: 0.08em; }
.hero-lede { max-width: 650px; margin-top: 3rem; color: var(--muted); font-size: clamp(1.05rem, 1.6vw, 1.35rem); }
.hero-actions { display: flex; flex-wrap: wrap; gap: 1rem; margin-top: 2.5rem; }
.button { padding: 0.85rem 1.3rem; border: 1px solid var(--accent); text-decoration: none; font-weight: 800; }
.button.primary { background: var(--accent); color: var(--ink); }

.product-section { padding: 110px 8vw; }
.section-kicker { color: var(--accent); font-size: 0.75rem; font-weight: 900; letter-spacing: 0.24em; text-transform: uppercase; }
.section-title { max-width: 850px; margin: 1.1rem 0 3.5rem; font-family: var(--display); font-size: clamp(2.5rem, 6vw, 5rem); line-height: 1.05; letter-spacing: -0.05em; }
.feature-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1px; background: var(--line); border: 1px solid var(--line); }
.feature { min-height: 270px; padding: 2rem; background: var(--ink); }
.feature-number { color: var(--accent); font-size: 0.72rem; font-weight: 900; letter-spacing: 0.2em; }
.feature h2 { margin: 4rem 0 1rem; font-size: 1.55rem; }
.feature p { color: var(--muted); }
.product-statement { display: grid; grid-template-columns: 0.8fr 1.2fr; gap: 8vw; align-items: end; }
.statement-mark { font-family: var(--display); font-size: clamp(7rem, 15vw, 13rem); color: var(--accent); line-height: 0.8; }
.statement-copy { font-size: clamp(1.5rem, 3.2vw, 3rem); font-weight: 750; line-height: 1.35; }
.statement-copy small { display: block; margin-top: 2rem; color: var(--muted); font-size: 0.95rem; font-weight: 500; }
.product-footer { display: flex; justify-content: space-between; gap: 2rem; padding: 2rem 8vw; border-top: 1px solid var(--line); color: var(--muted); font-size: 0.78rem; }
.product-footer a { text-decoration: none; }

/* 树蜘：深色网络科技 */
.theme-spider { --ink: #090a15; --paper: #eef7ff; --accent: #65e8ff; --muted: #8b96ad; --line: rgba(101, 232, 255, 0.17); --display: "Arial Black", "Microsoft YaHei", sans-serif; }
.theme-spider .brand-title { letter-spacing: 0.06em; }
.theme-spider .product-hero { background-image: linear-gradient(rgba(101,232,255,.07) 1px, transparent 1px), linear-gradient(90deg, rgba(101,232,255,.07) 1px, transparent 1px), radial-gradient(circle at 78% 48%, rgba(80,54,220,.35), transparent 27%); background-size: 72px 72px, 72px 72px, auto; }
.theme-spider .product-hero::before, .theme-spider .product-hero::after { content: ""; position: absolute; right: 10vw; top: 26%; width: min(34vw, 470px); aspect-ratio: 1; border: 1px solid var(--accent); border-radius: 50%; opacity: .45; box-shadow: 0 0 70px rgba(101,232,255,.12), inset 0 0 70px rgba(101,232,255,.08); }
.theme-spider .product-hero::after { right: 17vw; top: 38%; width: min(20vw, 280px); border-radius: 8px; transform: rotate(45deg); }
.theme-spider .feature:hover { background: #10152a; }

/* 树挚：温暖人文编辑风 */
.theme-bond { --ink: #eee8d8; --paper: #25302a; --accent: #7d1f2d; --muted: #686a5e; --line: rgba(37,48,42,.18); --display: Georgia, "Songti SC", "SimSun", serif; }
.theme-bond .product-header { background: rgba(238,232,216,.9); }
.theme-bond .product-hero { background: radial-gradient(circle at 74% 43%, rgba(125,31,45,.1) 0 19%, transparent 19.5%), radial-gradient(circle at 74% 43%, transparent 0 30%, rgba(125,31,45,.2) 30.3% 30.7%, transparent 31%), linear-gradient(110deg, transparent 0 63%, rgba(65,83,59,.08) 63%); }
.theme-bond .brand-title { letter-spacing: -0.03em; }
.theme-bond .brand-title span { font-family: var(--body); }
.theme-bond .feature { background: #eee8d8; }
.theme-bond .feature:hover { background: #e4dcc8; }
.theme-bond .statement-mark { font-family: Georgia, serif; font-style: italic; }

/* 树炙：高温动势与力量 */
.theme-flame { --ink: #120b08; --paper: #fff3df; --accent: #ff5a1f; --muted: #bca28f; --line: rgba(255,90,31,.25); --display: Impact, "Arial Black", "Microsoft YaHei", sans-serif; }
.theme-flame .product-hero { background: linear-gradient(118deg, transparent 0 52%, rgba(255,68,0,.1) 52%), radial-gradient(ellipse at 77% 78%, #ff3b00 0 5%, #ff8a00 6% 13%, rgba(255,90,31,.3) 14% 26%, transparent 43%); }
.theme-flame .product-hero::after { content: "HOT / BOLD / FORWARD"; position: absolute; right: -1rem; bottom: 8rem; color: rgba(255,90,31,.13); font-family: var(--display); font-size: clamp(4rem, 11vw, 10rem); line-height: .82; writing-mode: vertical-rl; }
.theme-flame .brand-title { letter-spacing: 0.06em; text-transform: uppercase; text-shadow: 8px 8px 0 rgba(255,90,31,.18); }
.theme-flame .feature { background: #120b08; transition: transform .25s, background .25s; }
.theme-flame .feature:hover { background: #22100a; transform: translateY(-8px); }

@media (max-width: 760px) {
    .product-header { grid-template-columns: auto 1fr; min-height: 68px; padding: 0 1rem; }
    .home-link { font-size: 0; }
    .home-link::before { content: "树知"; font-size: .78rem; }
    .header-mark { display: none; }
    .product-hero { padding: 118px 1.25rem 70px; }
    .brand-title { font-size: clamp(4.5rem, 31vw, 8rem); }
    .brand-title span { margin-top: 1.2rem; }
    .product-section { padding: 80px 1.25rem; }
    .feature-grid { grid-template-columns: 1fr; }
    .feature { min-height: auto; }
    .feature h2 { margin-top: 2rem; }
    .product-statement { grid-template-columns: 1fr; gap: 3rem; }
    .product-footer { flex-direction: column; padding: 2rem 1.25rem; }
    .theme-spider .product-hero::before, .theme-spider .product-hero::after { right: -25vw; width: 78vw; opacity: .22; }
}

@media (prefers-reduced-motion: no-preference) {
    .hero-copy { animation: rise-in .8s cubic-bezier(.2,.8,.2,1) both; }
    @keyframes rise-in { from { opacity: 0; transform: translateY(26px); } }
}