*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --bg: #f5f7fa;
  --surface: #ffffff;
  --text: #1f2937;
  --text-secondary: #6b7280;
  --primary: #6366f1;
  --primary-hover: #4f46e5;
  --border: #e5e7eb;
  --success: #10b981;
  --error: #ef4444;
  --radius: 12px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  line-height: 1.6;
}

nav {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 10;
}

.nav-inner {
  max-width: 960px;
  margin: 0 auto;
  padding: 0 20px;
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-weight: 700;
  font-size: 1.15rem;
  color: var(--primary);
  text-decoration: none;
}

#user-area {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 0.875rem;
}

#user-area .avatar {
  width: 30px;
  height: 30px;
  border-radius: 50%;
}

#user-area .username {
  color: var(--text-secondary);
}

.btn-logout {
  background: none;
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 4px 12px;
  cursor: pointer;
  font-size: 0.8rem;
  color: var(--text-secondary);
}

.btn-logout:hover {
  background: #f3f4f6;
}

main {
  flex: 1;
  max-width: 960px;
  margin: 0 auto;
  padding: 40px 20px;
  width: 100%;
}

.view {
  display: none;
}

.view.active {
  display: block;
}

.hidden {
  display: none !important;
}

/* Login */
.login-card {
  text-align: center;
  max-width: 420px;
  margin: 60px auto;
  padding: 48px 32px;
}

.login-card h1 {
  margin-bottom: 12px;
  font-size: 1.5rem;
}

.login-card p {
  color: var(--text-secondary);
  margin-bottom: 28px;
}

/* Cards */
.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
  margin-top: 24px;
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
}

.card-icon {
  font-size: 1.5rem;
  margin-bottom: 8px;
}

.card h3 {
  margin-bottom: 6px;
  font-size: 1.05rem;
}

.card > p {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: 16px;
}

/* Forms */
.feature-form {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.feature-form label {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-secondary);
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.feature-form input {
  padding: 8px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 0.9rem;
  outline: none;
  transition: border-color 0.15s;
}

.feature-form input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 2px rgba(99,102,241,0.15);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 20px;
  border: none;
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s;
}

.btn-primary {
  background: var(--primary);
  color: #fff;
}

.btn-primary:hover {
  background: var(--primary-hover);
}

.btn-primary:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* Result */
.result {
  margin-top: 12px;
  padding: 10px 12px;
  border-radius: 6px;
  font-size: 0.82rem;
  display: none;
}

.result.show {
  display: block;
}

.result.success {
  background: #ecfdf5;
  color: #065f46;
  border: 1px solid #a7f3d0;
}

.result.error {
  background: #fef2f2;
  color: #991b1b;
  border: 1px solid #fecaca;
}

/* Footer */
footer {
  text-align: center;
  padding: 20px;
  font-size: 0.8rem;
  color: var(--text-secondary);
}

/* Welcome */
.welcome h2 {
  font-size: 1.35rem;
}

.subtitle {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

/* Loading spinner */
.spinner {
  display: inline-block;
  width: 16px;
  height: 16px;
  border: 2px solid rgba(255,255,255,0.3);
  border-top-color: #fff;
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}