:root {
  --sidebar-bg: #171717;
  --bg: #f3f5f8;
  --panel: #ffffff;
  --line: #e4e8ef;
  --text: #111827;
  --muted: #677489;
  --accent: #10a37f;
}

* {
  box-sizing: border-box;
}

html,
body {
  height: 100%;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Noto Sans CJK SC", "Source Han Sans SC", "Microsoft YaHei UI", "Microsoft YaHei", "PingFang SC", "Hiragino Sans GB", sans-serif;
  color: var(--text);
  background: linear-gradient(180deg, #f8fafc 0%, var(--bg) 100%);
  -webkit-font-smoothing: antialiased;
}

button,
input,
select,
textarea {
  font: inherit;
}

button {
  border: 0;
  background: none;
  padding: 0;
}

.hidden {
  display: none !important;
}

.app-shell {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 316px minmax(0, 1fr);
}

.sidebar {
  min-width: 0;
  padding: 20px 18px;
  color: #f8fafc;
  background: linear-gradient(180deg, #1a1b1f 0%, var(--sidebar-bg) 100%);
}

.brand,
.header-main,
.header-thread-actions {
  display: flex;
  align-items: center;
}

.brand {
  gap: 14px;
}

.brand-mark {
  width: 50px;
  height: 50px;
  display: grid;
  place-items: center;
  border-radius: 16px;
  background: var(--accent);
  color: #f8fafc;
}

.brand-copy h1,
.header-copy h2 {
  margin: 0;
  font-size: 20px;
  line-height: 1.25;
}

.brand-tier {
  display: inline-flex;
  margin-top: 8px;
  padding: 6px 10px;
  border-radius: 999px;
  color: #d7fff4;
  background: rgba(16, 163, 127, 0.16);
  font-size: 12px;
}

.thread-create-btn,
.icon-btn,
.send-btn {
  cursor: pointer;
}

.workspace {
  min-width: 0;
  min-height: 100vh;
  display: grid;
  grid-template-rows: auto minmax(0, 1fr) auto;
}

.workspace-header {
  position: sticky;
  top: 0;
  z-index: 10;
  padding: 16px 24px;
  border-bottom: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.92);
}

.workspace-scroll {
  min-height: 0;
  overflow: auto;
  padding: 24px;
}

.welcome-panel {
  max-width: 960px;
  margin: 0 auto;
}

.hero-card,
.quick-panel,
.composer-card {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
}

.hero-card {
  padding: 28px;
}

.hero-card h3 {
  margin: 10px 0 0;
  font-size: 30px;
  line-height: 1.22;
}

.hero-badge {
  color: var(--accent);
  font-weight: 700;
}

.composer-wrap {
  padding: 0 24px 24px;
}

.composer-card {
  max-width: 960px;
  margin: 0 auto;
  padding: 14px;
}

.composer-input-shell textarea {
  width: 100%;
  min-height: 48px;
  resize: none;
  border: 0;
  outline: none;
  color: var(--text);
  background: transparent;
}

.send-btn {
  padding: 10px 16px;
  border-radius: 8px;
  color: #ffffff;
  background: var(--accent);
}

@media (max-width: 1040px) {
  .app-shell {
    grid-template-columns: minmax(0, 1fr);
  }

  .sidebar {
    display: none;
  }
}