* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: Arial, sans-serif;
  background: #111827;
  color: #111827;
}

.app {
  min-height: 100vh;
  padding: 20px;
}

.card {
  width: 100%;
  max-width: 420px;
  margin: 80px auto;
  padding: 24px;
  background: #ffffff;
  border-radius: 18px;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.35);
}

.brand h1 {
  margin: 0 0 8px;
  font-size: 28px;
}

.brand p {
  margin: 0 0 24px;
  color: #6b7280;
  line-height: 1.5;
}

.form {
  display: grid;
  gap: 16px;
}

label {
  display: grid;
  gap: 8px;
  font-weight: 700;
}

input {
  width: 100%;
  padding: 13px 14px;
  border: 1px solid #d1d5db;
  border-radius: 12px;
  font-size: 16px;
}

button {
  border: 0;
  border-radius: 12px;
  padding: 13px 16px;
  background: #2563eb;
  color: #ffffff;
  font-weight: 700;
  font-size: 16px;
  cursor: pointer;
}

button.secondary {
  background: #e5e7eb;
  color: #111827;
}

.message {
  min-height: 20px;
  color: #dc2626;
}

.hidden {
  display: none;
}

.dashboard {
  max-width: 1100px;
  margin: 0 auto;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 18px;
  padding: 18px;
  background: #ffffff;
  border-radius: 18px;
}

.topbar h1 {
  margin: 0 0 6px;
}

.topbar p {
  margin: 0;
  color: #6b7280;
}

.layout {
  display: grid;
  grid-template-columns: 340px 1fr;
  gap: 18px;
}

.email-list,
.email-detail {
  background: #ffffff;
  border-radius: 18px;
  overflow: hidden;
  min-height: 520px;
}

.email-item {
  display: block;
  width: 100%;
  padding: 16px;
  border: 0;
  border-bottom: 1px solid #e5e7eb;
  background: #ffffff;
  color: #111827;
  text-align: left;
  border-radius: 0;
}

.email-item:hover {
  background: #f3f4f6;
}

.email-item strong {
  display: block;
  margin-bottom: 6px;
}

.email-item span {
  display: block;
  color: #6b7280;
  font-size: 14px;
}

.email-detail {
  padding: 20px;
}

.email-header {
  border-bottom: 1px solid #e5e7eb;
  margin-bottom: 18px;
  padding-bottom: 18px;
}

.email-header h2 {
  margin: 0 0 10px;
}

.email-header p {
  margin: 4px 0;
  color: #6b7280;
}

.email-body {
  line-height: 1.6;
}

.email-frame {
  width: 100%;
  min-height: 420px;
  border: 0;
  background: #ffffff;
}

.empty {
  padding: 18px;
  color: #6b7280;
}

@media (max-width: 760px) {
  .app {
    padding: 12px;
  }

  .card {
    margin: 40px auto;
  }

  .topbar {
    align-items: flex-start;
    flex-direction: column;
  }

  .layout {
    grid-template-columns: 1fr;
  }

  .email-list,
  .email-detail {
    min-height: auto;
  }
}