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

:root {
  --bg-main: #f8fafc;
  --bg-card: rgba(255, 255, 255, 0.85);
  --bg-input: #ffffff;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --border: rgba(148, 163, 184, 0.2);
  --accent: #6366f1;
  --accent-light: #818cf8;
  --accent-glow: rgba(99, 102, 241, 0.3);
  --success: #10b981;
  --warning: #f59e0b;
  --danger: #ef4444;
  --card-shadow: 0 4px 24px rgba(0, 0, 0, 0.06);
  --hover-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
  --gradient-1: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --gradient-2: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
  --gradient-3: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
}

body.dark {
  --bg-main: #0f172a;
  --bg-card: rgba(30, 41, 59, 0.85);
  --bg-input: #1e293b;
  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --border: rgba(71, 85, 105, 0.4);
  --card-shadow: 0 4px 24px rgba(0, 0, 0, 0.3);
  --hover-shadow: 0 8px 32px rgba(0, 0, 0, 0.4);
}

body {
  font-family: 'Inter', sans-serif;
  background: var(--bg-main);
  min-height: 100vh;
  transition: background 0.4s ease;
}

.app-wrapper {
  min-height: 100vh;
  padding: 40px 20px;
  position: relative;
  overflow: hidden;
}

.background-shapes {
  position: fixed;
  inset: 0;
  pointer-events: none;
  overflow: hidden;
}

.shape {
  position: absolute;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.5;
  animation: float 20s ease-in-out infinite;
}

.shape-1 {
  width: 400px;
  height: 400px;
  background: var(--gradient-1);
  top: -100px;
  right: -100px;
}

.shape-2 {
  width: 300px;
  height: 300px;
  background: var(--gradient-2);
  bottom: -50px;
  left: -50px;
  animation-delay: -5s;
}

.shape-3 {
  width: 250px;
  height: 250px;
  background: var(--gradient-3);
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  animation-delay: -10s;
}

@keyframes float {
  0%, 100% { transform: translate(0, 0) scale(1); }
  33% { transform: translate(30px, -30px) scale(1.05); }
  66% { transform: translate(-20px, 20px) scale(0.95); }
}

.container {
  max-width: 580px;
  margin: 0 auto;
  background: var(--bg-card);
  backdrop-filter: blur(20px);
  border-radius: 24px;
  box-shadow: var(--card-shadow);
  border: 1px solid var(--border);
  padding: 32px;
  position: relative;
  transition: all 0.3s ease;
}

header {
  margin-bottom: 28px;
}

.header-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  display: flex;
  align-items: center;
  gap: 14px;
}

.logo-icon {
  width: 48px;
  height: 48px;
  background: var(--gradient-1);
  border-radius: 14px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  box-shadow: 0 4px 16px var(--accent-glow);
}

h1 {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.5px;
}

.tagline {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-top: 2px;
}

.theme-toggle {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 30px;
  padding: 8px 14px;
  cursor: pointer;
  transition: all 0.3s ease;
}

.theme-toggle:hover {
  box-shadow: var(--hover-shadow);
}

.toggle-track {
  width: 40px;
  height: 22px;
  background: var(--border);
  border-radius: 11px;
  position: relative;
  transition: background 0.3s;
}

.toggle-thumb {
  position: absolute;
  top: 3px;
  left: 3px;
  width: 16px;
  height: 16px;
  background: var(--accent);
  border-radius: 50%;
  transition: transform 0.3s cubic-bezier(0.68, -0.55, 0.27, 1.55);
}

body.dark .toggle-thumb {
  transform: translateX(18px);
}

.sun-icon, .moon-icon {
  font-size: 1rem;
  transition: opacity 0.3s;
}

.moon-icon { opacity: 0.4; }
.sun-icon { opacity: 1; }

body.dark .moon-icon { opacity: 1; }
body.dark .sun-icon { opacity: 0.4; }

.search-container {
  position: relative;
  margin-bottom: 20px;
}

.search-icon {
  position: absolute;
  left: 16px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1rem;
  opacity: 0.5;
}

.search-container input {
  width: 100%;
  padding: 14px 16px 14px 48px;
  background: var(--bg-input);
  border: 2px solid var(--border);
  border-radius: 14px;
  font-size: 0.95rem;
  color: var(--text-primary);
  transition: all 0.3s ease;
}

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

.search-container input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 4px var(--accent-glow);
}

.todo-form {
  margin-bottom: 24px;
}

.input-wrapper {
  display: flex;
  gap: 12px;
  margin-bottom: 14px;
}

#todoInput {
  flex: 1;
  padding: 16px 20px;
  background: var(--bg-input);
  border: 2px solid var(--border);
  border-radius: 14px;
  font-size: 1rem;
  color: var(--text-primary);
  transition: all 0.3s ease;
}

#todoInput::placeholder {
  color: var(--text-muted);
}

#todoInput:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 4px var(--accent-glow);
}

.add-btn {
  width: 54px;
  height: 54px;
  background: var(--gradient-1);
  border: none;
  border-radius: 14px;
  color: #fff;
  font-size: 1.75rem;
  font-weight: 300;
  cursor: pointer;
  transition: all 0.3s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 16px var(--accent-glow);
}

.add-btn:hover {
  transform: translateY(-2px) scale(1.05);
  box-shadow: 0 8px 24px var(--accent-glow);
}

.add-btn:active {
  transform: scale(0.95);
}

.form-options {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.option-group {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 8px 12px;
}

.option-group label {
  font-size: 0.9rem;
}

.option-group input,
.option-group select {
  border: none;
  background: transparent;
  color: var(--text-primary);
  font-size: 0.85rem;
  cursor: pointer;
}

.option-group input:focus,
.option-group select:focus {
  outline: none;
}

.priority-options {
  gap: 6px;
  padding: 8px 10px;
}

.priority-btn {
  width: 28px;
  height: 28px;
  border: 2px solid var(--border);
  border-radius: 50%;
  background: var(--bg-input);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s ease;
}

.priority-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
}

.priority-btn.low .priority-dot { background: var(--success); }
.priority-btn.medium .priority-dot { background: var(--warning); }
.priority-btn.high .priority-dot { background: var(--danger); }

.priority-btn.active {
  border-color: var(--accent);
  transform: scale(1.1);
}

.filters-wrapper {
  margin-bottom: 20px;
}

.status-tabs {
  display: flex;
  background: var(--bg-input);
  border-radius: 12px;
  padding: 4px;
  margin-bottom: 14px;
}

.tab-btn {
  flex: 1;
  padding: 10px 16px;
  border: none;
  background: transparent;
  border-radius: 10px;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.3s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
}

.tab-btn:hover {
  color: var(--text-primary);
}

.tab-btn.active {
  background: var(--accent);
  color: #fff;
  box-shadow: 0 2px 8px var(--accent-glow);
}

.tab-count {
  font-size: 0.75rem;
  padding: 2px 8px;
  background: rgba(255,255,255,0.2);
  border-radius: 10px;
}

.tab-btn:not(.active) .tab-count {
  background: var(--border);
}

.category-chips {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.chip {
  padding: 8px 14px;
  border: 1px solid var(--border);
  background: var(--bg-input);
  border-radius: 20px;
  font-size: 0.8rem;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.2s ease;
}

.chip:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.chip.active {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.progress-section {
  margin-bottom: 20px;
}

.progress-info {
  display: flex;
  justify-content: space-between;
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: 8px;
}

#progressPercent {
  font-weight: 600;
  color: var(--accent);
}

.progress-bar {
  height: 8px;
  background: var(--border);
  border-radius: 4px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: var(--gradient-1);
  border-radius: 4px;
  width: 0%;
  transition: width 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

.todo-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
  min-height: 100px;
}

.todo-item {
  display: flex;
  align-items: flex-start;
  gap: 14px;
  padding: 16px 18px;
  background: var(--bg-input);
  border-radius: 14px;
  border: 1px solid var(--border);
  animation: slideIn 0.4s cubic-bezier(0.4, 0, 0.2, 1);
  transition: all 0.3s ease;
  position: relative;
  overflow: hidden;
}

.todo-item::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 4px;
  background: var(--success);
}

.todo-item.priority-medium::before { background: var(--warning); }
.todo-item.priority-high::before { background: var(--danger); }

.todo-item:hover {
  transform: translateX(4px);
  box-shadow: var(--card-shadow);
}

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

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateY(-12px) scale(0.96);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

.check-btn {
  width: 24px;
  height: 24px;
  border: 2px solid var(--text-muted);
  border-radius: 8px;
  background: transparent;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  margin-top: 2px;
}

.check-btn:hover {
  border-color: var(--accent);
  background: var(--accent-glow);
}

.todo-item.completed .check-btn {
  background: var(--accent);
  border-color: var(--accent);
}

.check-btn::after {
  content: '✓';
  color: #fff;
  font-size: 14px;
  font-weight: 600;
  opacity: 0;
  transform: scale(0);
  transition: all 0.2s ease;
}

.todo-item.completed .check-btn::after {
  opacity: 1;
  transform: scale(1);
}

.todo-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 8px;
  min-width: 0;
}

.todo-text {
  font-size: 0.95rem;
  color: var(--text-primary);
  font-weight: 500;
  line-height: 1.4;
  transition: all 0.3s ease;
}

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

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

.meta-badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 4px 10px;
  border-radius: 8px;
  font-size: 0.75rem;
  font-weight: 500;
}

.meta-badge.category {
  background: var(--accent-glow);
  color: var(--accent);
}

.meta-badge.date {
  background: var(--border);
  color: var(--text-secondary);
}

.meta-badge.date.overdue {
  background: rgba(239, 68, 68, 0.15);
  color: var(--danger);
}

.delete-btn {
  background: none;
  border: none;
  width: 32px;
  height: 32px;
  border-radius: 8px;
  color: var(--text-muted);
  font-size: 1.2rem;
  cursor: pointer;
  opacity: 0;
  transition: all 0.2s ease;
  display: flex;
  align-items: center;
  justify-content: center;
}

.todo-item:hover .delete-btn {
  opacity: 1;
}

.delete-btn:hover {
  background: rgba(239, 68, 68, 0.1);
  color: var(--danger);
}

.empty-state {
  text-align: center;
  padding: 48px 20px;
  color: var(--text-muted);
}

.empty-state .empty-icon {
  font-size: 3rem;
  margin-bottom: 16px;
  opacity: 0.5;
}

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

.no-results {
  text-align: center;
  padding: 32px;
  color: var(--text-secondary);
}

footer {
  text-align: center;
  margin-top: 28px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
}

footer p {
  font-size: 0.85rem;
  color: var(--text-muted);
}

@media (max-width: 500px) {
  .container {
    padding: 24px 18px;
    border-radius: 20px;
  }
  
  .form-options {
    flex-direction: column;
  }
  
  .option-group {
    width: 100%;
  }
  
  .priority-options {
    justify-content: center;
  }
  
  .category-chips {
    justify-content: center;
  }
}