/* ===== RESET & BASE ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --color-bg: #0d0f1a;
  --color-surface: rgba(255, 255, 255, 0.06);
  --color-surface-hover: rgba(255, 255, 255, 0.1);
  --color-border: rgba(255, 255, 255, 0.1);
  --color-border-focus: rgba(139, 92, 246, 0.6);

  --color-primary: #8b5cf6;
  --color-primary-light: #a78bfa;
  --color-primary-dark: #6d28d9;
  --color-accent: #ec4899;
  --color-success: #34d399;
  --color-danger: #f87171;

  --color-text: #f1f5f9;
  --color-text-muted: #94a3b8;
  --color-text-faint: #475569;

  --font-main: 'Noto Sans TC', 'Inter', sans-serif;
  --radius-sm: 10px;
  --radius-md: 16px;
  --radius-lg: 24px;
  --radius-full: 9999px;

  --shadow-glow: 0 0 40px rgba(139, 92, 246, 0.15);
  --shadow-card: 0 8px 32px rgba(0, 0, 0, 0.4);
  --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-main);
  background-color: var(--color-bg);
  color: var(--color-text);
  min-height: 100vh;
  display: flex;
  align-items: flex-start;
  justify-content: center;
  padding: 40px 16px 80px;
  overflow-x: hidden;
  position: relative;
}

/* ===== BACKGROUND ORBS ===== */
.bg-orbs {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  overflow: hidden;
}

.orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(100px);
  opacity: 0.35;
  animation: float 12s ease-in-out infinite;
}

.orb-1 {
  width: 520px;
  height: 520px;
  background: radial-gradient(circle, #8b5cf6, #6d28d9);
  top: -180px;
  left: -120px;
  animation-delay: 0s;
}

.orb-2 {
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, #ec4899, #be185d);
  bottom: -100px;
  right: -100px;
  animation-delay: -4s;
}

.orb-3 {
  width: 300px;
  height: 300px;
  background: radial-gradient(circle, #06b6d4, #0891b2);
  top: 50%;
  left: 60%;
  animation-delay: -8s;
}

@keyframes float {
  0%, 100% { transform: translateY(0px) scale(1); }
  33% { transform: translateY(-30px) scale(1.05); }
  66% { transform: translateY(20px) scale(0.97); }
}

/* ===== APP CONTAINER ===== */
.app-container {
  position: relative;
  z-index: 1;
  width: 100%;
  max-width: 560px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

/* ===== HEADER ===== */
.app-header {
  text-align: center;
  padding: 32px 0 16px;
}

.header-icon {
  font-size: 2rem;
  background: linear-gradient(135deg, var(--color-primary-light), var(--color-accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  display: block;
  margin-bottom: 12px;
  animation: spin-slow 20s linear infinite;
}

@keyframes spin-slow {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

.app-title {
  font-size: 2.4rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  background: linear-gradient(135deg, #f1f5f9 30%, #a78bfa 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1.2;
}

.app-subtitle {
  margin-top: 8px;
  font-size: 0.95rem;
  color: var(--color-text-muted);
  font-weight: 300;
  letter-spacing: 0.03em;
}

/* ===== STATS BAR ===== */
.stats-bar {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 16px 32px;
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  box-shadow: var(--shadow-card);
}

.stat-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  flex: 1;
}

.stat-number {
  font-size: 1.8rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--color-primary-light), var(--color-accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1;
  transition: var(--transition);
}

.stat-label {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  font-weight: 500;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.stat-divider {
  width: 1px;
  height: 36px;
  background: var(--color-border);
  flex-shrink: 0;
}

/* ===== INPUT SECTION ===== */
.input-section {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 8px;
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  box-shadow: var(--shadow-card);
  transition: border-color var(--transition), box-shadow var(--transition);
}

.input-section:focus-within {
  border-color: var(--color-border-focus);
  box-shadow: var(--shadow-card), 0 0 0 3px rgba(139, 92, 246, 0.1);
}

.input-wrapper {
  display: flex;
  align-items: center;
  gap: 8px;
}

.input-icon {
  font-size: 1.3rem;
  color: var(--color-text-muted);
  padding: 0 8px 0 12px;
  flex-shrink: 0;
  user-select: none;
}

.todo-input {
  flex: 1;
  background: transparent;
  border: none;
  outline: none;
  color: var(--color-text);
  font-family: var(--font-main);
  font-size: 0.975rem;
  padding: 12px 4px;
  caret-color: var(--color-primary-light);
}

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

.add-btn {
  position: relative;
  overflow: hidden;
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  color: white;
  border: none;
  border-radius: var(--radius-md);
  padding: 10px 22px;
  font-family: var(--font-main);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  transition: transform var(--transition), box-shadow var(--transition), opacity var(--transition);
  flex-shrink: 0;
  letter-spacing: 0.02em;
}

.add-btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 8px 20px rgba(139, 92, 246, 0.4);
}

.add-btn:active {
  transform: translateY(0px) scale(0.97);
}

.btn-ripple {
  position: absolute;
  inset: 0;
  background: rgba(255, 255, 255, 0.15);
  border-radius: inherit;
  opacity: 0;
  transition: opacity 0.3s;
}

.add-btn:active .btn-ripple {
  opacity: 1;
}

/* ===== FILTER SECTION ===== */
.filter-section {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.filter-tabs {
  display: flex;
  gap: 4px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  padding: 4px;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.filter-tab {
  background: transparent;
  border: none;
  color: var(--color-text-muted);
  font-family: var(--font-main);
  font-size: 0.82rem;
  font-weight: 500;
  padding: 7px 16px;
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: background var(--transition), color var(--transition), transform var(--transition);
  white-space: nowrap;
}

.filter-tab:hover:not(.active) {
  background: var(--color-surface-hover);
  color: var(--color-text);
}

.filter-tab.active {
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  color: white;
  box-shadow: 0 4px 12px rgba(139, 92, 246, 0.35);
}

.clear-btn {
  background: transparent;
  border: 1px solid var(--color-border);
  color: var(--color-text-muted);
  font-family: var(--font-main);
  font-size: 0.8rem;
  font-weight: 500;
  padding: 7px 14px;
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: background var(--transition), color var(--transition), border-color var(--transition);
  white-space: nowrap;
}

.clear-btn:hover {
  background: rgba(248, 113, 113, 0.12);
  border-color: rgba(248, 113, 113, 0.4);
  color: var(--color-danger);
}

/* ===== TODO LIST ===== */
.todo-list-section {
  min-height: 120px;
}

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

/* ===== TODO ITEM ===== */
.todo-item {
  display: flex;
  align-items: center;
  gap: 14px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 14px 16px;
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.25);
  animation: slide-in 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
  transition: background var(--transition), border-color var(--transition), transform var(--transition), box-shadow var(--transition);
  position: relative;
  overflow: hidden;
}

.todo-item::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 3px;
  background: linear-gradient(180deg, var(--color-primary), var(--color-accent));
  opacity: 0;
  transition: opacity var(--transition);
  border-radius: 0 2px 2px 0;
}

.todo-item:hover {
  background: var(--color-surface-hover);
  border-color: rgba(255, 255, 255, 0.15);
  transform: translateX(3px);
  box-shadow: 0 6px 24px rgba(0, 0, 0, 0.3);
}

.todo-item:hover::before {
  opacity: 1;
}

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

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

.todo-item.removing {
  animation: slide-out 0.3s cubic-bezier(0.4, 0, 1, 1) forwards;
}

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

@keyframes slide-out {
  from {
    opacity: 1;
    transform: translateX(0) scale(1);
    max-height: 80px;
  }
  to {
    opacity: 0;
    transform: translateX(40px) scale(0.9);
    max-height: 0;
    padding-top: 0;
    padding-bottom: 0;
    margin: 0;
  }
}

/* ===== CHECKBOX ===== */
.todo-checkbox {
  appearance: none;
  -webkit-appearance: none;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  border: 2px solid rgba(139, 92, 246, 0.5);
  cursor: pointer;
  flex-shrink: 0;
  position: relative;
  transition: background var(--transition), border-color var(--transition), transform var(--transition);
}

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

.todo-checkbox:checked {
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  border-color: transparent;
}

.todo-checkbox:checked::after {
  content: '✓';
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 12px;
  font-weight: 700;
}

/* ===== TODO TEXT ===== */
.todo-text {
  flex: 1;
  font-size: 0.94rem;
  font-weight: 400;
  color: var(--color-text);
  line-height: 1.5;
  transition: color var(--transition);
  word-break: break-word;
}

/* ===== TODO ACTIONS ===== */
.todo-actions {
  display: flex;
  gap: 6px;
  opacity: 0;
  transition: opacity var(--transition);
  flex-shrink: 0;
}

.todo-item:hover .todo-actions {
  opacity: 1;
}

.action-btn {
  background: transparent;
  border: none;
  padding: 5px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 0.9rem;
  transition: background var(--transition), transform var(--transition);
  color: var(--color-text-muted);
  line-height: 1;
}

.action-btn:hover {
  background: var(--color-surface-hover);
  transform: scale(1.15);
}

.action-btn.delete:hover {
  background: rgba(248, 113, 113, 0.15);
  color: var(--color-danger);
}

/* ===== EMPTY STATE ===== */
.empty-state {
  display: none;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 60px 24px;
  text-align: center;
  animation: fade-in 0.4s ease;
}

.empty-state.visible {
  display: flex;
}

.empty-icon {
  font-size: 3rem;
  margin-bottom: 16px;
  animation: sway 3s ease-in-out infinite;
}

@keyframes sway {
  0%, 100% { transform: rotate(-5deg); }
  50% { transform: rotate(5deg); }
}

.empty-text {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--color-text-muted);
  margin-bottom: 6px;
}

.empty-sub {
  font-size: 0.85rem;
  color: var(--color-text-faint);
}

@keyframes fade-in {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ===== SCROLLBAR ===== */
::-webkit-scrollbar {
  width: 6px;
}
::-webkit-scrollbar-track {
  background: transparent;
}
::-webkit-scrollbar-thumb {
  background: rgba(139, 92, 246, 0.3);
  border-radius: 3px;
}
::-webkit-scrollbar-thumb:hover {
  background: rgba(139, 92, 246, 0.5);
}

/* ===== RESPONSIVE ===== */
@media (max-width: 480px) {
  body { padding: 24px 12px 60px; }
  .app-title { font-size: 1.8rem; }
  .stats-bar { padding: 14px 20px; }
  .stat-number { font-size: 1.5rem; }
  .filter-section { flex-wrap: wrap; }
  .filter-tabs { flex: 1; justify-content: center; }
  .clear-btn { flex: 1; text-align: center; }
}