:root {
  --bg-color: #0d1117;
  --bg-gradient: radial-gradient(circle at 15% 50%, rgba(44, 44, 60, 0.4), transparent 50%),
                 radial-gradient(circle at 85% 30%, rgba(20, 60, 90, 0.3), transparent 50%);
  --glass-bg: rgba(255, 255, 255, 0.03);
  --glass-border: rgba(255, 255, 255, 0.08);
  --text-primary: #e6edf3;
  --text-secondary: #8b949e;
  --accent-color: #58a6ff;
  --accent-hover: #79c0ff;
  --danger-color: #ff7b72;
  --success-color: #3fb950;
  --past-date-bg: rgba(255, 123, 114, 0.15);
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

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

body {
  font-family: var(--font-family);
  background-color: var(--bg-color);
  background-image: var(--bg-gradient);
  background-attachment: fixed;
  color: var(--text-primary);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  line-height: 1.6;
}

header {
  padding: 1.5rem 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--glass-border);
  background: rgba(13, 17, 23, 0.7);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  position: sticky;
  top: 0;
  z-index: 100;
}

header h1 {
  font-size: 1.5rem;
  font-weight: 600;
  background: -webkit-linear-gradient(0deg, #58a6ff, #a371f7);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  letter-spacing: -0.5px;
}

nav a {
  color: var(--text-secondary);
  text-decoration: none;
  margin-left: 1.5rem;
  font-weight: 500;
  transition: color 0.2s ease;
}

nav a:hover {
  color: var(--text-primary);
}

main {
  flex: 1;
  padding: 3rem 1.5rem;
  max-width: 800px;
  margin: 0 auto;
  width: 100%;
  animation: fadeIn 0.6s ease-out;
}

.glass-panel {
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: 16px;
  padding: 2.5rem;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  margin-bottom: 2rem;
}

h2 {
  font-size: 1.8rem;
  font-weight: 600;
  margin-bottom: 1rem;
}

p.subtitle {
  color: var(--text-secondary);
  margin-bottom: 2rem;
}

.input-group {
  margin-bottom: 1.5rem;
}

label {
  display: block;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: 0.5rem;
}

input[type="text"],
input[type="date"] {
  width: 100%;
  padding: 0.75rem 1rem;
  border-radius: 8px;
  border: 1px solid var(--glass-border);
  background: rgba(0, 0, 0, 0.2);
  color: var(--text-primary);
  font-family: inherit;
  font-size: 1rem;
  transition: border-color 0.2s, box-shadow 0.2s;
}

input[type="text"]:focus,
input[type="date"]:focus {
  outline: none;
  border-color: var(--accent-color);
  box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.15);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.75rem 1.5rem;
  border-radius: 8px;
  border: none;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  font-family: inherit;
}

.btn-primary {
  background-color: var(--accent-color);
  color: #000;
}

.btn-primary:hover {
  background-color: var(--accent-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(88, 166, 255, 0.2);
}

.btn-secondary {
  background-color: transparent;
  color: var(--text-primary);
  border: 1px solid var(--glass-border);
}

.btn-secondary:hover {
  background-color: rgba(255, 255, 255, 0.05);
  border-color: var(--text-secondary);
}

.btn-danger {
  background-color: transparent;
  color: var(--danger-color);
  border: 1px solid rgba(255, 123, 114, 0.3);
}

.btn-danger:hover {
  background-color: rgba(255, 123, 114, 0.1);
  border-color: var(--danger-color);
}

.auth-form {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

/* Dates List */
.date-list {
  list-style: none;
  margin-top: 1.5rem;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 1rem;
}

.date-item {
  background: rgba(0, 0, 0, 0.2);
  border: 1px solid var(--glass-border);
  border-radius: 8px;
  padding: 0.75rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: transform 0.2s;
}

.date-item:hover {
  border-color: var(--text-secondary);
}

.date-item.past {
  background: var(--past-date-bg);
  border-color: rgba(255, 123, 114, 0.4);
}

.date-item.new-date {
  background: rgba(63, 185, 80, 0.1);
  border-color: rgba(63, 185, 80, 0.4);
}

.date-item.deleted-date {
  background: rgba(255, 123, 114, 0.05);
  border-color: rgba(255, 123, 114, 0.3);
  opacity: 0.8;
}

.date-item button.remove-btn {
  background: none;
  border: none;
  color: var(--text-secondary);
  cursor: pointer;
  font-size: 1.2rem;
  line-height: 1;
  padding: 0 0.2rem;
  transition: color 0.2s;
}

.date-item button.remove-btn:hover {
  color: var(--danger-color);
}

.date-item button.remove-btn.undo-btn:hover {
  color: var(--success-color);
}

.alert {
  padding: 1rem;
  border-radius: 8px;
  margin-bottom: 1.5rem;
  font-size: 0.9rem;
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
}

.alert-warning {
  background: rgba(210, 153, 34, 0.1);
  border: 1px solid rgba(210, 153, 34, 0.4);
  color: #e3b341;
}

.alert-error {
  background: rgba(255, 123, 114, 0.1);
  border: 1px solid rgba(255, 123, 114, 0.4);
  color: #ff7b72;
}

.hidden {
  display: none !important;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Toggle Switch */
.switch {
  position: relative;
  display: inline-block;
  width: 50px;
  height: 28px;
}

.switch input {
  opacity: 0;
  width: 0;
  height: 0;
}

.slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(255,255,255,0.1);
  transition: .4s;
  border-radius: 28px;
  border: 1px solid var(--glass-border);
}

.slider:before {
  position: absolute;
  content: "";
  height: 20px;
  width: 20px;
  left: 3px;
  bottom: 3px;
  background-color: var(--text-secondary);
  transition: .4s;
  border-radius: 50%;
}

input:checked + .slider {
  background-color: rgba(88, 166, 255, 0.2);
  border-color: var(--accent-color);
}

input:checked + .slider:before {
  transform: translateX(22px);
  background-color: var(--accent-color);
}

/* PWA Update Toast */
.update-toast {
  position: fixed;
  bottom: 24px;
  right: 24px;
  background: rgba(13, 17, 23, 0.95);
  border: 1px solid var(--accent-color);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.5);
  padding: 1rem 1.5rem;
  border-radius: 12px;
  display: flex;
  align-items: center;
  gap: 1.5rem;
  z-index: 1000;
  transform: translateY(150%);
  transition: transform 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
}

.update-toast.show {
  transform: translateY(0);
}

.update-toast span {
  font-weight: 500;
}

.update-toast .btn {
  padding: 0.5rem 1rem;
  font-size: 0.9rem;
}