:root {
  --primary: #6366f1;
  --primary-dark: #4f46e5;
  --accent: #8b5cf6;
  --accent-light: #a78bfa;
  --background: #f8f7ff;
  --surface: #ffffff;
  --text-primary: #1a1a2e;
  --text-secondary: #6b7280;
  --text-muted: #9ca3af;
  --border: #e5e7eb;
  --success: #10b981;
  --success-light: #d1fae5;
  --danger: #ef4444;
  --danger-light: #fee2e2;
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  scroll-behavior: smooth;
}

body {
  background: linear-gradient(135deg, var(--background) 0%, #f3f0ff 100%);
  font-family: "DM Sans", sans-serif;
  color: var(--text-primary);
  min-height: 100vh;
  padding: 20px;
}

.container {
  max-width: 800px;
  margin: 0 auto;
}

/* Header */
.header {
  text-align: center;
  margin-bottom: 50px;
  animation: fadeInDown 0.6s ease;
}

.header-content {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 8px;
}

.logo svg {
  color: var(--primary);
}

.logo h1 {
  font-family: "Clash Display", sans-serif;
  font-size: 2.5rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.02em;
}

.tagline {
  font-size: 1rem;
  color: var(--text-secondary);
  font-weight: 500;
}

/* Main */
.main {
  display: flex;
  flex-direction: column;
  gap: 32px;
}

/* Input Section */
.input-section {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.input-wrapper {
  display: flex;
  gap: 12px;
  background: var(--surface);
  padding: 16px;
  border-radius: 16px;
  box-shadow: var(--shadow-md);
  border: 1px solid var(--border);
  transition: var(--transition);
}

.input-wrapper:focus-within {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1), var(--shadow-md);
}

.todo-input {
  flex: 1;
  border: none;
  background: transparent;
  font-size: 1rem;
  font-family: inherit;
  color: var(--text-primary);
  outline: none;
}

.todo-input::placeholder {
  color: var(--text-muted);
}

.add-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 20px;
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
  color: white;
  border: none;
  border-radius: 12px;
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  transition: var(--transition);
  white-space: nowrap;
}

.add-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 16px rgba(99, 102, 241, 0.3);
}

.add-btn:active {
  transform: translateY(0);
}

/* Filter Buttons */
.filter-buttons {
  display: flex;
  gap: 12px;
  justify-content: center;
}

.filter-btn {
  padding: 8px 16px;
  background: var(--surface);
  color: var(--text-secondary);
  border: 1px solid var(--border);
  border-radius: 12px;
  font-weight: 500;
  font-size: 0.9rem;
  cursor: pointer;
  transition: var(--transition);
}

.filter-btn:hover {
  border-color: var(--primary);
  color: var(--primary);
}

.filter-btn.active {
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
  color: white;
  border-color: transparent;
}

/* Stats Section */
.stats-section {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 16px;
}

.stat-card {
  background: var(--surface);
  padding: 24px;
  border-radius: 16px;
  text-align: center;
  border: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
}

.stat-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
  border-color: var(--primary);
}

.stat-number {
  font-family: "Clash Display", sans-serif;
  font-size: 2.5rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.stat-label {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-top: 8px;
  font-weight: 500;
}

/* Todo List Container */
.todo-list-container {
  background: var(--surface);
  border-radius: 16px;
  border: 1px solid var(--border);
  box-shadow: var(--shadow-md);
  overflow: hidden;
  min-height: 300px;
  display: flex;
  flex-direction: column;
}

.todo-list {
  list-style: none;
  flex: 1;
}

.todo-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 16px;
  border-bottom: 1px solid var(--border);
  transition: var(--transition);
  animation: slideIn 0.3s ease;
}

.todo-item:last-child {
  border-bottom: none;
}

.todo-item:hover {
  background: var(--background);
}

.todo-item.completed {
  opacity: 0.6;
}

.todo-item.completed .todo-text {
  text-decoration: line-through;
  color: var(--text-muted);
}

/* Checkbox */
.checkbox {
  width: 24px;
  height: 24px;
  min-width: 24px;
  border: 2px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
  background: transparent;
}

.checkbox:hover {
  border-color: var(--primary);
}

.todo-item.completed .checkbox {
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
  border-color: transparent;
}

.checkbox svg {
  width: 14px;
  height: 14px;
  color: white;
  opacity: 0;
  transition: var(--transition);
}

.todo-item.completed .checkbox svg {
  opacity: 1;
}

/* Todo Text */
.todo-text {
  flex: 1;
  font-size: 1rem;
  color: var(--text-primary);
  word-break: break-word;
}

/* Delete Button */
.delete-btn {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: transparent;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  border-radius: 8px;
  transition: var(--transition);
}

.delete-btn:hover {
  background: var(--danger-light);
  color: var(--danger);
}

/* Empty State */
.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 16px;
  padding: 60px 20px;
  color: var(--text-muted);
  text-align: center;
}

.empty-state svg {
  color: var(--text-muted);
}

.empty-state p {
  font-size: 1rem;
  font-weight: 500;
}

/* Action Bar */
.action-bar {
  display: flex;
  justify-content: center;
}

.clear-btn {
  padding: 12px 24px;
  background: var(--danger-light);
  color: var(--danger);
  border: 1px solid var(--danger);
  border-radius: 12px;
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  transition: var(--transition);
}

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

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

/* Animations */
@keyframes fadeInDown {
  from {
    opacity: 0;
    transform: translateY(-20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateX(-20px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

/* Responsive */
@media (max-width: 768px) {
  .logo h1 {
    font-size: 2rem;
  }

  .input-wrapper {
    flex-direction: column;
  }

  .add-btn {
    width: 100%;
    justify-content: center;
  }

  .stats-section {
    grid-template-columns: 1fr;
  }

  .filter-buttons {
    flex-wrap: wrap;
  }

  .filter-btn {
    flex: 1;
    min-width: 100px;
  }

  .todo-item {
    padding: 12px;
    gap: 10px;
  }

  .todo-text {
    font-size: 0.95rem;
  }
}

@media (max-width: 480px) {
  body {
    padding: 12px;
  }

  .header {
    margin-bottom: 32px;
  }

  .logo h1 {
    font-size: 1.75rem;
  }

  .tagline {
    font-size: 0.9rem;
  }

  .stat-number {
    font-size: 2rem;
  }

  .main {
    gap: 24px;
  }
}