* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
  }
  
  :root {
    --bg: #f0f2f5;
    --surface: #ffffff;
    --surface-hover: #f5f5f5;
    --text: #333333;
    --text-muted: #666666;
    --accent: #5c7cfa;
    --accent-hover: #7b95ff;
    --danger: #d9534f;
    --danger-hover: #e06e6e;
    --border: #e0e0e0;
    --radius: 10px;
    --shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
  }

  body.dark-mode {
    --bg: #1a1d23;
    --surface: #252932;
    --surface-hover: #2e333d;
    --text: #e8eaed;
    --text-muted: #9aa0a6;
    --accent: #7c9ce0;
    --accent-hover: #8fade8;
    --danger: #e07a7a;
    --danger-hover: #e89090;
    --border: #3d424b;
    --shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
  }
  
  body {
    font-family: "Pretendard", "Malgun Gothic", sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    padding: 2rem 1rem;
    line-height: 1.5;
    transition: background 0.3s ease, color 0.3s ease;
  }
  
  .app {
    max-width: 480px;
    margin: 0 auto;
  }
  
  .header {
    text-align: center;
    margin-bottom: 2rem;
    position: relative;
  }
  
  .header h1 {
    font-size: 1.75rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    margin-bottom: 0.25rem;
  }
  
  .subtitle {
    font-size: 0.9rem;
    color: var(--text-muted);
  }

  .theme-toggle {
    position: absolute;
    top: 0;
    right: 0;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 0.5rem 0.75rem;
    cursor: pointer;
    font-size: 1.2rem;
    transition: background 0.2s, border-color 0.2s, color 0.2s;
    display: flex;
    align-items: center;
    justify-content: center;
  }

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

  .theme-toggle .icon {
    transition: transform 0.3s ease;
  }

  body.dark-mode .theme-toggle .icon {
    transform: rotate(360deg);
  }
  
  .input-section {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
  }
  
  #taskInput {
    flex: 1;
    padding: 0.75rem 1rem;
    font-size: 1rem;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    background: var(--surface);
    color: var(--text);
    outline: none;
    transition: border-color 0.2s, box-shadow 0.2s;
  }
  
  #taskInput::placeholder {
    color: var(--text-muted);
  }
  
  #taskInput:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(124, 156, 224, 0.2);
  }
  
  #addBtn {
    padding: 0.75rem 1.25rem;
    font-size: 1rem;
    font-weight: 600;
    border: none;
    border-radius: var(--radius);
    background: var(--accent);
    color: #fff;
    cursor: pointer;
    transition: background 0.2s, transform 0.1s;
    white-space: nowrap;
  }
  
  #addBtn:hover {
    background: var(--accent-hover);
  }
  
  #addBtn:active {
    transform: scale(0.98);
  }
  
  .tasks-section {
    display: flex;
    flex-direction: column;
    gap: 2rem;
    margin-bottom: 1.5rem;
  }
  
  .tasks-group {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
  }
  
  .tasks-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text);
    margin-bottom: 0.25rem;
  }
  
  .task-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    min-height: 2rem;
  }
  
  .task-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.875rem 1rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    transition: background 0.2s, border-color 0.2s;
  }
  
  .task-item:hover {
    background: var(--surface-hover);
  }
  
  .task-item.done .task-text {
    text-decoration: line-through;
    color: var(--text-muted);
  }
  
  .task-checkbox {
    width: 20px;
    height: 20px;
    accent-color: var(--accent);
    cursor: pointer;
    flex-shrink: 0;
  }
  
  .task-text {
    flex: 1;
    word-break: break-word;
    transition: color 0.2s, text-decoration 0.2s;
  }
  
  .task-delete {
    padding: 0.35rem 0.65rem;
    font-size: 0.8rem;
    font-weight: 500;
    border: none;
    border-radius: 6px;
    background: transparent;
    color: var(--danger);
    cursor: pointer;
    transition: background 0.2s, color 0.2s;
    flex-shrink: 0;
  }
  
  .task-delete:hover {
    background: rgba(224, 122, 122, 0.15);
    color: var(--danger-hover);
  }
  
  .footer {
    margin-top: 1.5rem;
    text-align: center;
    font-size: 0.875rem;
    color: var(--text-muted);
  }
  
  #pendingList:empty::before {
    content: "예정된 할 일이 없습니다.";
    display: block;
    text-align: center;
    padding: 2rem 1rem;
    color: var(--text-muted);
    font-size: 0.9rem;
  }
  
  #completedList:empty::before {
    content: "완료된 할 일이 없습니다.";
    display: block;
    text-align: center;
    padding: 2rem 1rem;
    color: var(--text-muted);
    font-size: 0.9rem;
  }
  /* Add styles here */