:root {
  --bg-primary: #F8FAFB;
  --bg-surface: #FFFFFF;
  --text-primary: #1A1A1A;
  --text-secondary: #666666;
  --accent: #607afb;
  --border: #E0E0E0;
  --hover: #F5F5F5;
  --completed-bg: #EEF1FF;
  --completed-text: #4C5FD5;
  --transition-speed: 300ms;
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

.dark {
  --bg-primary: #121212;
  --bg-surface: #1E1E1E;
  --text-primary: #E0E0E0;
  --text-secondary: #999999;
  --accent: #7B93FF;
  --border: #333333;
  --hover: #2A2A2A;
  --completed-bg: rgba(96, 122, 251, 0.15);
  --completed-text: #8FA5FF;
}

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

body {
  font-family: var(--font-family);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  transition: background-color var(--transition-speed) ease, color var(--transition-speed) ease;
}

.app {
  min-height: 100vh;
  background-color: var(--bg-primary);
  transition: background-color var(--transition-speed) ease;
}

.header {
  background-color: var(--bg-surface);
  border-bottom: 1px solid var(--border);
  padding: 24px 48px;
  position: sticky;
  top: 0;
  z-index: 100;
  transition: all var(--transition-speed) ease;
}

.header-content {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo-section {
  display: flex;
  align-items: center;
  gap: 12px;
}

.logo-icon {
  width: 32px;
  height: 32px;
  color: var(--accent);
}

.app-title {
  font-size: 28px;
  font-weight: bold;
  color: var(--text-primary);
  transition: color var(--transition-speed) ease;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 16px;
}

.today-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text-secondary);
  font-size: 14px;
  cursor: pointer;
  transition: all 200ms ease;
  height: 40px;
}

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

.today-btn svg {
  width: 16px;
  height: 16px;
}

.theme-toggle {
  padding: 8px 16px;
  border-radius: 8px;
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-secondary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 200ms ease;
  font-size: 14px;
  height: 40px;
}

.theme-toggle:hover {
  background-color: var(--hover);
  border-color: var(--accent);
  color: var(--accent);
  transform: scale(1.1);
}

.theme-toggle:active {
  transform: scale(0.95);
}

.theme-icon {
  width: 20px;
  height: 20px;
  transition: transform 500ms ease;
}

.theme-icon.rotated {
  transform: rotate(360deg);
}

.main {
  padding: 40px 0;
}

.container {
  max-width: 800px;
  margin: 0 auto;
  padding: 0 32px;
}

.content-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 32px;
}

.section-title {
  font-size: 32px;
  font-weight: bold;
  color: var(--text-primary);
  transition: color var(--transition-speed) ease;
}

.date-display {
  font-size: 16px;
  font-weight: 500;
  color: var(--accent);
}

.task-input-container {
  margin-bottom: 24px;
}

.task-input {
  width: 100%;
  padding: 16px 20px;
  font-size: 16px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background-color: var(--bg-surface);
  color: var(--text-primary);
  transition: all 300ms cubic-bezier(0.4, 0, 0.2, 1);
  font-family: var(--font-family);
}

.task-input:focus {
  outline: none;
  border: 1px solid var(--border);
  background-color: var(--bg-primary);
  box-shadow: 0 8px 24px rgba(96, 122, 251, 0.12), 0 4px 8px rgba(0, 0, 0, 0.06);
  transform: scale(1.01);
}

.task-input::placeholder {
  color: var(--text-secondary);
}

.task-stats {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 24px;
  opacity: 0;
  transition: opacity 300ms ease;
}

.task-stats.visible {
  opacity: 1;
}

.task-count {
  font-size: 14px;
  color: var(--text-secondary);
  font-weight: 500;
}

.clear-completed {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  font-size: 14px;
  cursor: pointer;
  padding: 4px 8px;
  border-radius: 4px;
  transition: all 200ms ease;
}

.clear-completed:hover {
  color: var(--accent);
  background-color: var(--hover);
}

.task-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
  min-height: 400px;
  position: relative;
}

.task-item {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 16px 20px;
  background-color: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  cursor: grab;
  transition: all 300ms ease;
  position: relative;
}

.task-item:active {
  cursor: grabbing;
}

.task-item.dragging {
  opacity: 0.4;
  cursor: grabbing;
}

.task-item.drag-over::before {
  content: '';
  position: absolute;
  top: -6px;
  left: 0;
  right: 0;
  height: 3px;
  background-color: var(--accent);
  border-radius: 2px;
  box-shadow: 0 0 8px rgba(96, 122, 251, 0.4);
  z-index: 10;
}

.task-item:hover {
  background-color: var(--hover);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.task-item.completed {
  background-color: var(--completed-bg);
  opacity: 0.8;
}

.checkbox {
  width: 24px;
  height: 24px;
  border: 2px solid var(--border);
  border-radius: 6px;
  background: transparent;
  cursor: pointer;
  display: block;
  transition: all 300ms ease;
  flex-shrink: 0;
  position: relative;
}

.checkbox:hover {
  border-color: var(--accent);
  transform: scale(1.1);
}

.checkbox.checked {
  background-color: var(--accent);
  border-color: var(--accent);
  transform: scale(1.1);
}

.checkbox.checked:hover {
  transform: scale(1.2);
}

.checkmark {
  width: 16px;
  height: 16px;
  color: white;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.task-text {
  flex: 1;
  font-size: 16px;
  color: var(--text-primary);
  transition: all 300ms ease;
  word-break: break-word;
}

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

.delete-btn {
  width: 32px;
  height: 32px;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  cursor: pointer;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: all 200ms ease;
  flex-shrink: 0;
}

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

.delete-btn:hover {
  background-color: rgba(244, 67, 54, 0.1);
  color: #f44336;
  transform: scale(1.1);
}

.delete-btn svg {
  width: 16px;
  height: 16px;
}

.loading-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: var(--bg-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
}

.loading {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
}

.loading-logo {
  width: 60px;
  height: 60px;
  color: var(--accent);
  animation: pulse 1.5s ease-in-out infinite;
}

@keyframes pulse {
  0%, 100% {
    opacity: 1;
    transform: scale(1);
  }
  50% {
    opacity: 0.5;
    transform: scale(0.95);
  }
}

.loading-text {
  color: var(--text-secondary);
  font-size: 14px;
  font-weight: 500;
}

.empty-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--text-secondary);
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.lottie-animation {
  width: 200px;
  height: 200px;
  margin: 0 auto 24px;
}

.empty-state p {
  font-size: 16px;
  margin: 0;
}

@media (max-width: 768px) {
  .header {
    padding: 16px 24px;
  }

  .header-content {
    flex-direction: column;
    gap: 16px;
    align-items: flex-start;
  }

  .header-actions {
    width: 100%;
    justify-content: space-between;
  }

  .container {
    padding: 0 24px;
  }

  .content-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 8px;
  }

  .section-title {
    font-size: 28px;
  }

  .task-item {
    padding: 20px;
    min-height: 48px;
  }

  .task-input {
    padding: 20px;
    font-size: 18px;
  }
}

@media (max-width: 480px) {
  .header {
    padding: 12px 16px;
  }

  .container {
    padding: 0 16px;
  }

  .task-item {
    padding: 16px;
  }

  .task-input {
    padding: 16px;
  }
}

.checkbox:focus-visible,
.delete-btn:focus-visible,
.theme-toggle:focus-visible,
.today-btn:focus-visible,
.clear-completed:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

html {
  scroll-behavior: smooth;
}