:root {
  --bg1: #f6f8fc;
  --bg2: #eef2ff;
  --card: #ffffff;
  --line: #dfe4ef;
  --text: #111827;
  --sub: #64748b;
  --primary: #1f3a8a;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  min-height: 100vh;
  font-family: "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  color: var(--text);
  background: radial-gradient(circle at 8% 0%, var(--bg2), var(--bg1) 48%, #ffffff 100%);
}
.auth-page, .mode-page {
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 20px;
}
.auth-card {
  width: min(420px, 100%);
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  box-shadow: 0 14px 32px rgba(15,23,42,.08);
  padding: 22px;
  display: grid;
  gap: 12px;
}
.auth-card h1 { margin: 0; font-size: 30px; letter-spacing: -.02em; }
.auth-card p { margin: 0; color: var(--sub); font-size: 14px; }
label { display: grid; gap: 6px; font-size: 13px; color: #334155; }
input {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 10px 12px;
  font-size: 14px;
  outline: none;
}
input:focus { border-color: #a9b7dc; box-shadow: 0 0 0 3px rgba(59, 130, 246, .15); }
.btn {
  border: 1px solid var(--line);
  border-radius: 10px;
  background: #fff;
  color: var(--text);
  font-weight: 700;
  padding: 10px 14px;
  cursor: pointer;
}
.btn.primary { border-color: var(--primary); background: var(--primary); color: #fff; }
.msg { min-height: 20px; font-size: 13px; color: #b42318; }
.links { font-size: 13px; color: var(--sub); }
.links a { color: #2748a5; text-decoration: none; }
.links a:hover { text-decoration: underline; }
.row-auth { display: flex; gap: 8px; }
.avatar-preview-wrap { display: flex; justify-content: center; }
.avatar-preview {
  width: 84px;
  height: 84px;
  border-radius: 50%;
  border: 1px solid var(--line);
  background: #f8fbff;
  display: grid;
  place-items: center;
  font-size: 32px;
  color: #1f3a8a;
  font-weight: 700;
  overflow: hidden;
}
.avatar-preview img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.mode-page { width: min(1100px, 100%); margin: 0 auto; align-content: start; gap: 16px; }
.mode-top {
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 16px;
}
.mode-top h1 { margin: 0; }
.mode-top p { margin: 6px 0 0; color: var(--sub); }
.mode-grid {
  width: 100%;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}
.mode-card {
  border-radius: 18px;
  border: 1px solid #d9e0ef;
  padding: 22px;
  min-height: 220px;
  display: grid;
  align-content: space-between;
  box-shadow: 0 14px 28px rgba(18, 25, 42, .08);
}
.mode-card.single { background: linear-gradient(130deg, #f8fbff, #edf4ff); }
.mode-card.online { background: linear-gradient(130deg, #f8f7ff, #eef0ff); }
.mode-card h2 { margin: 0; font-size: 30px; letter-spacing: -.01em; }
.mode-card p { margin: 8px 0 18px; color: #475569; }
@media (max-width: 900px) {
  .mode-grid { grid-template-columns: 1fr; }
}

@media (max-width: 768px) {
  .auth-page, .mode-page {
    padding: 12px;
  }
  .auth-card {
    border-radius: 14px;
    padding: 16px;
    gap: 10px;
  }
  .auth-card h1 {
    font-size: 26px;
    line-height: 1.15;
  }
  .mode-page {
    gap: 12px;
  }
  .mode-top {
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
    padding: 12px;
  }
  .mode-top h1 {
    font-size: 28px;
    line-height: 1.15;
  }
  .mode-card {
    min-height: 180px;
    padding: 16px;
    border-radius: 14px;
  }
  .mode-card h2 {
    font-size: 24px;
  }
  .mode-card p {
    font-size: 14px;
    margin-bottom: 12px;
  }
  .btn {
    min-height: 38px;
    font-size: 14px;
    padding: 8px 12px;
  }
}

@media (max-width: 480px) {
  .auth-card h1 { font-size: 24px; }
  .mode-top h1 { font-size: 24px; }
  .row-auth { flex-direction: column; }
}