:root {
    color-scheme: light;
    --bg: #f6f7f9;
    --panel: #ffffff;
    --line: #d8dde6;
    --text: #1f2937;
    --muted: #6b7280;
    --accent: #0f766e;
    --accent-strong: #115e59;
    --danger: #b42318;
}

* { box-sizing: border-box; }
body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", sans-serif;
    color: var(--text);
    background: var(--bg);
}

.app-shell {
    display: grid;
    grid-template-columns: 300px 1fr;
    min-height: 100vh;
}

.sidebar {
    display: flex;
    flex-direction: column;
    gap: 14px;
    border-right: 1px solid var(--line);
    background: #fbfcfd;
    padding: 18px;
}

.brand { display: flex; justify-content: space-between; align-items: baseline; gap: 8px; }
.brand span, .hint, #status { color: var(--muted); font-size: 13px; }

button {
    border: 0;
    border-radius: 6px;
    background: var(--accent);
    color: #fff;
    padding: 10px 14px;
    cursor: pointer;
    font-weight: 650;
}
button:hover { background: var(--accent-strong); }
button:disabled { opacity: .6; cursor: wait; }

input, textarea {
    width: 100%;
    border: 1px solid var(--line);
    border-radius: 6px;
    padding: 10px 12px;
    color: var(--text);
    background: #fff;
    font: inherit;
}
textarea { resize: none; line-height: 1.55; }

.conversation-list { overflow: auto; display: grid; gap: 6px; }
.conversation {
    display: block;
    color: var(--text);
    text-decoration: none;
    padding: 9px 10px;
    border-radius: 6px;
    border: 1px solid transparent;
}
.conversation.active, .conversation:hover { background: #eef6f5; border-color: #c7e4df; }

.knowledge-panel {
    border-top: 1px solid var(--line);
    padding-top: 12px;
    display: grid;
    gap: 10px;
}
.knowledge-panel h2 { margin: 0; font-size: 15px; }
#uploadForm { display: grid; gap: 8px; }
#documentList { display: grid; gap: 5px; color: var(--muted); font-size: 13px; }
.logout { margin-top: auto; color: var(--muted); text-decoration: none; }

.chat {
    display: grid;
    grid-template-rows: auto 1fr auto;
    min-width: 0;
}
.toolbar {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 14px 18px;
    border-bottom: 1px solid var(--line);
    background: var(--panel);
}
.toolbar label:first-child { display: flex; align-items: center; gap: 8px; }
.toolbar input[type="text"], .toolbar input:not([type]) { width: 220px; }
.check { display: flex; align-items: center; gap: 6px; white-space: nowrap; }
.check input { width: auto; }

.messages {
    overflow: auto;
    padding: 26px min(7vw, 76px);
    display: flex;
    flex-direction: column;
    gap: 16px;
}
.message {
    max-width: 880px;
    line-height: 1.7;
    white-space: pre-wrap;
    border: 1px solid var(--line);
    background: var(--panel);
    border-radius: 8px;
    padding: 14px 16px;
}
.message.user { align-self: flex-end; background: #eef6f5; border-color: #c7e4df; }
.message.assistant { align-self: flex-start; }
.message .role { display: block; color: var(--muted); font-size: 12px; margin-bottom: 6px; }

.composer {
    display: grid;
    grid-template-columns: 1fr auto;
    gap: 12px;
    padding: 16px 18px;
    border-top: 1px solid var(--line);
    background: var(--panel);
}

.login-page {
    min-height: 100vh;
    display: grid;
    place-items: center;
}
.login-panel {
    width: min(380px, calc(100vw - 32px));
    display: grid;
    gap: 14px;
    padding: 28px;
    background: var(--panel);
    border: 1px solid var(--line);
    border-radius: 8px;
}
.login-panel h1 { margin: 0 0 4px; font-size: 24px; }
.login-panel label { display: grid; gap: 6px; }
.error { margin: 0; color: var(--danger); }

@media (max-width: 820px) {
    .app-shell { grid-template-columns: 1fr; }
    .sidebar { min-height: auto; border-right: 0; border-bottom: 1px solid var(--line); }
    .toolbar { flex-wrap: wrap; }
    .composer { grid-template-columns: 1fr; }
}