:root {
    --primary: #4F46E5;
    --primary-dark: #3730A3;
    --accent: #0891B2;
    --background: #F8FAFC;
    --surface: #FFFFFF;
    --text: #111827;
    --muted: #4B5563;
    --border: #D1D5DB;
    --success: #047857;
    --danger: #B91C1C;
    --shadow: 0 18px 50px rgba(30, 41, 59, 0.09);
    color-scheme: light;
}

* { box-sizing: border-box; }

body {
    margin: 0;
    min-width: 320px;
    background:
        radial-gradient(circle at 85% 5%, rgba(8, 145, 178, 0.12), transparent 28rem),
        linear-gradient(180deg, #EEF2FF 0, var(--background) 30rem);
    color: var(--text);
    font-family: "Microsoft YaHei UI", "PingFang SC", system-ui, sans-serif;
    line-height: 1.65;
}

button, input, select, textarea { font: inherit; }
button, select { cursor: pointer; }
a { color: var(--primary-dark); }

.skip-link {
    position: fixed;
    left: 1rem;
    top: -4rem;
    z-index: 20;
    padding: .7rem 1rem;
    background: var(--text);
    color: white;
}
.skip-link:focus { top: 1rem; }

.topbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1240px;
    margin: 0 auto;
    padding: 1.1rem 1.5rem;
}

.brand { display: flex; align-items: center; gap: .75rem; }
.brand-mark {
    display: grid;
    place-items: center;
    width: 2.7rem;
    height: 2.7rem;
    border-radius: .9rem;
    color: white;
    background: linear-gradient(135deg, var(--primary), var(--accent));
    font-weight: 800;
}
.brand strong, .brand small { display: block; }
.brand small { color: var(--muted); font-size: .76rem; }
.user-state { color: var(--muted); font-size: .9rem; }

.page-shell { max-width: 1240px; margin: 0 auto; padding: 0 1.5rem 3rem; }
.hero {
    display: flex;
    align-items: flex-end;
    justify-content: space-between;
    gap: 2rem;
    padding: 3.5rem 0 2.5rem;
}
.hero h1 { max-width: 760px; margin: .45rem 0 .75rem; font-size: clamp(2.1rem, 5vw, 4.2rem); line-height: 1.12; letter-spacing: -.04em; }
.hero p { max-width: 720px; margin: 0; color: var(--muted); font-size: 1.03rem; }
.eyebrow { color: var(--primary-dark); font-size: .77rem; font-weight: 800; letter-spacing: .12em; text-transform: uppercase; }
.compliance-chip { flex: 0 0 auto; padding: .7rem 1rem; border: 1px solid #A5B4FC; border-radius: 999px; background: rgba(255,255,255,.72); color: var(--primary-dark); font-size: .82rem; }

.app-grid { display: grid; grid-template-columns: 330px minmax(0, 1fr); gap: 1.25rem; align-items: start; }
.side-stack { display: grid; gap: 1.25rem; }
.card { border: 1px solid rgba(209, 213, 219, .9); border-radius: 1.2rem; background: rgba(255,255,255,.94); box-shadow: var(--shadow); }
.auth-card, .service-card { padding: 1.25rem; }
.chat-card { min-height: 650px; padding: 1.5rem; }
.section-heading { display: flex; align-items: center; justify-content: space-between; gap: 1rem; }
.section-heading h2, .service-card h2, .feedback-section h2 { margin: 0; font-size: 1.18rem; }
.chat-heading { padding-bottom: 1rem; border-bottom: 1px solid var(--border); }
.chat-heading h2 { margin: .1rem 0 0; font-size: 1.65rem; }

.tab-list { display: grid; grid-template-columns: 1fr 1fr; gap: .35rem; margin: 1rem 0; padding: .25rem; border-radius: .75rem; background: #EEF2FF; }
.tab-button { border: 0; border-radius: .55rem; padding: .55rem; background: transparent; color: var(--muted); }
.tab-button.active { background: white; color: var(--primary-dark); box-shadow: 0 2px 8px rgba(30,41,59,.08); font-weight: 700; }
.form-stack { display: grid; gap: .85rem; }
label { display: grid; gap: .35rem; color: #374151; font-size: .86rem; font-weight: 650; }
input, select, textarea { width: 100%; border: 1px solid var(--border); border-radius: .7rem; padding: .72rem .8rem; background: white; color: var(--text); }
textarea { resize: vertical; }
input:focus, select:focus, textarea:focus, button:focus-visible, a:focus-visible { outline: 3px solid rgba(79, 70, 229, .24); outline-offset: 2px; border-color: var(--primary); }
.check-row { display: flex; align-items: flex-start; gap: .5rem; font-weight: 500; line-height: 1.4; }
.check-row input { width: 1rem; height: 1rem; margin-top: .15rem; accent-color: var(--primary); }
.primary-button, .secondary-button { border: 0; border-radius: .72rem; padding: .72rem 1rem; font-weight: 750; }
.primary-button { background: linear-gradient(135deg, var(--primary), var(--primary-dark)); color: white; }
.secondary-button { background: #E0F2FE; color: #155E75; }
.link-button { border: 0; padding: 0; background: transparent; color: var(--primary-dark); }
.form-message { min-height: 1.4rem; margin: .65rem 0 0; color: var(--danger); font-size: .83rem; }
.form-message.success { color: var(--success); }
.account-summary { margin-top: 1rem; padding: .85rem; border-radius: .75rem; background: #EEF2FF; }
.hidden { display: none !important; }

.info-list { margin: .75rem 0 0; }
.info-list div { display: flex; justify-content: space-between; gap: 1rem; padding: .5rem 0; border-bottom: 1px solid #E5E7EB; }
.info-list dt { color: var(--muted); }
.info-list dd { margin: 0; text-align: right; font-weight: 700; }
.fine-print { color: var(--muted); font-size: .76rem; line-height: 1.55; }

.provider-select { min-width: 170px; }
.conversation { display: flex; flex-direction: column; gap: 1rem; min-height: 300px; max-height: 540px; overflow-y: auto; padding: 1.25rem 0; }
.message { max-width: 86%; padding: 1rem; border-radius: 1rem; }
.message-content { margin-top: .45rem; overflow-x: auto; overflow-wrap: anywhere; }
.message-content > :first-child { margin-top: 0; }
.message-content > :last-child { margin-bottom: 0; }
.message-content p { margin: .55rem 0; }
.user-message .message-content { white-space: pre-wrap; }
.message-content h3, .message-content h4, .message-content h5, .message-content h6 { margin: .9rem 0 .45rem; line-height: 1.35; }
.message-content ul, .message-content ol { margin: .55rem 0; padding-left: 1.35rem; }
.message-content li + li { margin-top: .25rem; }
.message-content blockquote { margin: .65rem 0; padding: .55rem .8rem; border-left: 4px solid var(--accent); background: rgba(255,255,255,.62); color: var(--muted); }
.message-content code { border-radius: .3rem; padding: .08rem .3rem; background: rgba(15,23,42,.09); font-family: Consolas, "Cascadia Code", monospace; font-size: .88em; }
.message-content pre { overflow-x: auto; margin: .7rem 0; border-radius: .7rem; padding: .85rem; background: #0F172A; color: #E2E8F0; }
.message-content pre code { padding: 0; background: transparent; color: inherit; }
.message-content table { width: 100%; margin: .7rem 0; border-collapse: collapse; background: white; font-size: .9em; }
.message-content th, .message-content td { border: 1px solid var(--border); padding: .45rem .55rem; text-align: left; vertical-align: top; }
.message-content th { background: #E0F2FE; color: #155E75; }
.message-content hr { margin: .9rem 0; border: 0; border-top: 1px solid var(--border); }
.message-content a { color: #0E7490; text-decoration-thickness: .08em; text-underline-offset: .16em; }
.system-message { align-self: flex-start; background: #F1F5F9; border: 1px solid #E2E8F0; }
.user-message { align-self: flex-end; background: var(--primary); color: white; }
.ai-message { align-self: flex-start; background: #ECFEFF; border: 1px solid #A5F3FC; }
.refusal-message { align-self: flex-start; background: #FFF7ED; border: 1px solid #FED7AA; }
.message-label { display: inline-flex; padding: .14rem .48rem; border-radius: 999px; background: var(--accent); color: white; font-size: .72rem; font-weight: 800; letter-spacing: .04em; }
.system-message .message-label { background: #475569; }
.refusal-message .message-label { background: #C2410C; }
.copy-button { margin-top: .75rem; border: 1px solid #67E8F9; border-radius: .5rem; padding: .35rem .65rem; background: white; color: #155E75; font-size: .78rem; }
.composer { border-top: 1px solid var(--border); padding-top: 1rem; }
.quick-questions { margin-bottom: 1rem; }
.quick-questions > span { display: block; margin-bottom: .45rem; color: var(--muted); font-size: .8rem; font-weight: 700; }
.quick-question-list { display: flex; flex-wrap: wrap; gap: .5rem; }
.quick-question { border: 1px solid #C7D2FE; border-radius: 999px; padding: .42rem .72rem; background: #EEF2FF; color: var(--primary-dark); font-size: .78rem; }
.quick-question:hover { border-color: var(--primary); background: #E0E7FF; }
.confirmations { display: flex; flex-wrap: wrap; gap: .75rem 1.5rem; margin: .75rem 0; }
.composer-footer { display: flex; justify-content: space-between; align-items: center; gap: 1rem; }
#char-count { color: var(--muted); font-size: .8rem; }

.feedback-section { display: grid; grid-template-columns: .8fr 1.2fr; gap: 2rem; margin-top: 1.25rem; padding: 1.5rem; }
.feedback-section p { color: var(--muted); }
.feedback-form { display: grid; grid-template-columns: 1fr 1fr; gap: .8rem; }
.feedback-form label:nth-child(2) { grid-column: 1 / -1; }
.feedback-form .secondary-button { align-self: end; }

footer { padding: 2.5rem 1.5rem 3.5rem; text-align: center; color: var(--muted); font-size: .82rem; }
footer nav { display: flex; justify-content: center; flex-wrap: wrap; gap: 1.2rem; }

.legal-shell { max-width: 860px; margin: 0 auto; padding: 2rem 1.5rem 4rem; }
.legal-shell article { padding: clamp(1.3rem, 4vw, 3rem); }
.legal-shell h1 { line-height: 1.2; }
.legal-shell h2 { margin-top: 2rem; font-size: 1.2rem; }
.legal-shell li { margin-bottom: .5rem; }
.back-link { display: inline-block; margin-bottom: 1rem; }
.notice-box { padding: 1rem; border-left: 4px solid var(--accent); background: #ECFEFF; }

@media (max-width: 860px) {
    .hero { align-items: flex-start; flex-direction: column; padding-top: 2rem; }
    .app-grid, .feedback-section { grid-template-columns: 1fr; }
    .side-stack { grid-template-columns: 1fr 1fr; }
    .chat-card { min-height: auto; }
}

@media (max-width: 600px) {
    .topbar { padding: .9rem 1rem; }
    .brand small, .user-state { display: none; }
    .page-shell { padding: 0 1rem 2rem; }
    .hero h1 { font-size: 2.25rem; }
    .side-stack { grid-template-columns: 1fr; }
    .chat-heading { align-items: flex-start; flex-direction: column; }
    .provider-select { width: 100%; }
    .message { max-width: 96%; }
    .confirmations { display: grid; }
    .feedback-form { grid-template-columns: 1fr; }
    .feedback-form label:nth-child(2) { grid-column: auto; }
}