:root {
  --primary-color: #4a6fa5;
  --secondary-color: #7ea6d9;
  --accent-color: #ff8c69;
  --background-color: #f0f2f5;
  --text-color: #1a1a1a;
  --light-text: #666;
  --danger-color: #e74c3c;
  --success-color: #2ecc71;
  --border-color: #ddd;
  --card-bg: rgba(255, 255, 255, 0.75);
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
  --blur: blur(15px);
}

[data-theme="dark"] {
  --primary-color: #3b5998;
  --secondary-color: #5c79b3;
  --accent-color: #ffa07a;
  --background-color: #121212;
  --text-color: #f0f0f0;
  --light-text: #999;
  --card-bg: rgba(45, 45, 45, 0.75);
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.4);
  --blur: blur(10px);
}

body {
  background: var(--background-color);
  color: var(--text-color);
  font-family: 'Segoe UI', sans-serif;
  transition: all 0.3s ease;
}

.container {
  max-width: 1200px;
  margin: auto;
  padding: 2rem;
  animation: fadeInBody 0.5s ease-in;
}

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

header {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 30px;
  padding: 15px 20px;
  border-radius: 15px;
  background: linear-gradient(145deg, var(--primary-color), var(--secondary-color));
  color: white;
  box-shadow: var(--shadow);
}

.logo {
  font-size: 28px;
  font-weight: bold;
  letter-spacing: 1px;
}

.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.nav-btn {
  background: rgba(255, 255, 255, 0.1);
  color: white;
  border: 1px solid rgba(255,255,255,0.2);
  padding: 10px 16px;
  font-size: 15px;
  border-radius: 10px;
  transition: background 0.3s, transform 0.2s;
  backdrop-filter: var(--blur);
}

.nav-btn:hover {
  background: rgba(255, 255, 255, 0.25);
  transform: translateY(-2px);
}

.nav-btn.active {
  background-color: white;
  color: var(--primary-color);
  font-weight: bold;
}

.view {
  display: none;
}

.view.active-view {
  display: block;
  animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: scale(0.98); }
  to { opacity: 1; transform: scale(1); }
}

/* Home Stats */
.stats-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
}

.stat-card {
  background: var(--card-bg);
  border-radius: 15px;
  padding: 30px 20px;
  text-align: center;
  box-shadow: var(--shadow);
  backdrop-filter: var(--blur);
}

.stat-card h3 {
  font-size: 18px;
  color: var(--light-text);
}

.stat-card p {
  font-size: 40px;
  color: var(--primary-color);
  font-weight: bold;
}

/* Forms & Inputs */
.form-group {
  margin-bottom: 25px;
}

.form-control {
  width: 100%;
  padding: 12px;
  font-size: 16px;
  border: 1px solid var(--border-color);
  border-radius: 10px;
  background-color: var(--card-bg);
  box-shadow: inset 0 1px 2px rgba(0,0,0,0.05);
  transition: border-color 0.3s;
}

.form-control:focus {
  outline: none;
  border-color: var(--primary-color);
}

/* Buttons */
.btn {
  padding: 10px 20px;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  font-weight: bold;
  transition: transform 0.2s ease, background-color 0.3s;
}

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

.btn-secondary {
  background: var(--secondary-color);
  color: white;
}

.btn-danger {
  background: var(--danger-color);
  color: white;
}

.btn:hover {
  transform: translateY(-1px);
  filter: brightness(1.1);
}

/* Category/Topic/Todo Section */
.active-section {
  background-color: rgba(74, 111, 165, 0.1);
  padding: 15px;
  border-radius: 10px;
  margin-top: 10px;
}

#todos-list li {
  background: var(--card-bg);
  margin-bottom: 10px;
  padding: 15px;
  border-radius: 10px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  box-shadow: var(--shadow);
  transition: transform 0.2s ease;
}

#todos-list li:hover {
  transform: scale(1.02);
}

/* View Structure */
.todo-structure {
  background: var(--card-bg);
  padding: 25px;
  border-radius: 15px;
  margin-bottom: 25px;
  box-shadow: var(--shadow);
  backdrop-filter: var(--blur);
}

/* Modal */
.modal.active {
  display: flex;
}

.modal-content {
  background-color: var(--card-bg);
  box-shadow: 0 0 40px var(--primary-color);
  padding: 30px;
  border-radius: 15px;
  width: 90%;
  max-width: 500px;
  animation: pulse 1.5s infinite alternate;
}

@keyframes pulse {
  from { box-shadow: 0 0 10px var(--accent-color); }
  to { box-shadow: 0 0 25px var(--accent-color); }
}

.timer-display {
  font-size: 48px;
  color: var(--accent-color);
  text-align: center;
  font-family: monospace;
}

/* Toast */
#toast {
  background-color: var(--success-color);
  color: white;
  font-weight: bold;
  padding: 12px 24px;
  border-radius: 10px;
  box-shadow: var(--shadow);
  transform: translateY(100px);
  opacity: 0;
  transition: all 0.4s ease;
}

#toast.show {
  opacity: 1;
  transform: translateY(0);
}