:root{
    --bg: #f7fafc;
    --card: #ffffff;
    --muted: #6b7280;
    --accent: #059669;
    --danger: #ef4444;
    --shadow: 0 6px 18px rgba(15,23,42,0.06);
    --radius: 12px;
    font-family: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial;
  }
  
  *{box-sizing:border-box}
  html,body{height:100%;margin:0;background:var(--bg);color:#0f172a}
  .container{
    max-width:720px;
    margin:48px auto;
    padding:24px;
  }
  
  /* Header */
  .header h1{margin:0;font-size:2rem;letter-spacing:-0.02em}
  .subtitle{margin:6px 0 0;color:var(--muted);font-size:0.95rem}
  
  /* Add task */
  .add-task{
    display:flex;
    gap:12px;
    margin-top:20px;
    align-items:center;
  }
  #task-input{
    flex:1;
    padding:12px 14px;
    border-radius:10px;
    border:1px solid #e6eef4;
    background:var(--card);
    box-shadow:var(--shadow);
    font-size:1rem;
  }
  .btn{
    background:var(--accent);
    color:#fff;
    border:none;
    padding:10px 16px;
    border-radius:10px;
    cursor:pointer;
    font-weight:600;
  }
  .btn:hover{transform:translateY(-1px)}
  
  /* Controls */
  .controls{
    display:flex;
    justify-content:space-between;
    align-items:center;
    margin:16px 0;
    gap:12px;
  }
  .filters{display:flex;gap:8px}
  .filter{
    background:transparent;
    border:1px solid transparent;
    color:var(--muted);
    padding:6px 10px;
    border-radius:8px;
    cursor:pointer;
  }
  .filter.active{background:#ecfdf5;color:var(--accent);border:1px solid rgba(5,150,105,0.12)}
  
  /* Task list */
  .task-list{list-style:none;padding:0;margin:0}
  .task{
    display:flex;
    align-items:center;
    gap:12px;
    background:var(--card);
    padding:12px;
    border-radius:10px;
    margin-bottom:10px;
    box-shadow:var(--shadow);
  }
  .task .toggle{width:18px;height:18px}
  .task-text{
    flex:1;
    font-size:1rem;
    word-break:break-word;
  }
  .task.completed .task-text{
    text-decoration:line-through;
    color:var(--muted);
    opacity:0.8;
  }
  .delete{
    background:transparent;
    border:none;
    color:var(--danger);
    font-size:20px;
    cursor:pointer;
    padding:4px;
  }

  .hidden {
    display: none;
  }
  
  /* Footer */
  .footer{
    margin-top:18px;
    display:flex;
    justify-content:flex-end;
  }
  .link{
    background:transparent;
    border:none;
    color:var(--muted);
    cursor:pointer;
  }
  
  /* Accessibility helper */
  .visually-hidden{
    position:absolute!important;
    height:1px;width:1px;
    overflow:hidden;clip:rect(1px,1px,1px,1px);
    white-space:nowrap;border:0;padding:0;margin:-1px;
  }
  
  /* Responsive */
  @media (max-width:520px){
    .container{padding:16px;margin:20px}
    .add-task{flex-direction:column;align-items:stretch}
    .btn{width:100%}
    .controls{flex-direction:column;align-items:stretch;gap:8px}
  }