:root{
    --bg: #14181c;
    --panel: #1d242c;
    --panel-border: #37414d;
    --text: #f5f6f7;
    --text-muted: #adb6c2;
    --accent: #eeb15f;
    --accent-2: #5cc9bd;
    --accent-3: #e0895f;
    --danger: #e2725a;
    --ok: #6fc98a;
    --sunken: #10141a;
    --hover-bg: #252d37;
  }
  :root[data-theme="light"]{
    --bg: #f3f4f6;
    --panel: #ffffff;
    --panel-border: #d7dbe1;
    --text: #1b2027;
    --text-muted: #5b6472;
    --accent: #c0791e;
    --accent-2: #0f8f83;
    --accent-3: #bc5a30;
    --danger: #c23f2a;
    --ok: #2f8f52;
    --sunken: #eef1f4;
    --hover-bg: #eef0f2;
  }
  *{box-sizing:border-box;}
  body{
    margin:0;
    background:var(--bg);
    color:var(--text);
    font-family:'IBM Plex Sans KR', sans-serif;
    font-size:17px;
    line-height:1.6;
    -webkit-font-smoothing:antialiased;
    transition:background 0.15s ease, color 0.15s ease;
  }
  .wrap{max-width:760px;margin:0 auto;padding:88px 20px 90px;}

  header{margin-bottom:40px;}

  /* 개별 계산기 페이지용 브랜드 스트립 + 브레드크럼 */
  .brand-strip{ margin-bottom:28px; }
  .brand-strip .brand-link{
    text-decoration:none;
    font-family:'IBM Plex Mono', monospace;
    font-size:14px;
    color:var(--accent-2);
    letter-spacing:0.02em;
  }
  .breadcrumb{
    margin-top:10px;
    font-size:13px;
    color:var(--text-muted);
  }
  .breadcrumb a{ color:var(--text-muted); text-decoration:none; }
  .breadcrumb a:hover{ color:var(--accent-2); }
  .breadcrumb .sep{ margin:0 6px; }

  .related-block{
    margin-top:36px;
    padding-top:24px;
    border-top:1px solid var(--panel-border);
  }
  .related-block h2{
    font-size:15px;
    font-weight:600;
    color:var(--text-muted);
    text-transform:uppercase;
    letter-spacing:0.04em;
    margin:0 0 14px;
  }
  .related-list{
    display:flex;
    flex-wrap:wrap;
    gap:10px;
  }
  .related-list a{
    display:block;
    background:var(--panel);
    border:1px solid var(--panel-border);
    border-radius:8px;
    padding:10px 14px;
    font-size:14px;
    color:var(--text);
    text-decoration:none;
  }
  .related-list a:hover{ border-color:var(--accent-2); color:var(--accent-2); }

  /* 홈(디렉토리) 페이지 */
  .home-intro{ margin-bottom:36px; }
  .home-category{ margin-bottom:32px; }
  .home-category h2{
    font-family:'IBM Plex Mono', monospace;
    font-size:13px;
    font-weight:600;
    letter-spacing:0.06em;
    text-transform:uppercase;
    color:var(--accent-2);
    margin:0 0 14px;
  }
  .home-grid{
    display:grid;
    grid-template-columns:repeat(auto-fill, minmax(220px, 1fr));
    gap:12px;
  }
  .home-card{
    display:block;
    background:var(--panel);
    border:1px solid var(--panel-border);
    border-radius:10px;
    padding:16px;
    text-decoration:none;
  }
  .home-card:hover{ border-color:var(--accent-2); }
  .home-card .card-title{
    font-size:15px;
    font-weight:600;
    color:var(--text);
    margin-bottom:6px;
  }
  .home-card:hover .card-title{ color:var(--accent-2); }
  .home-card .card-desc{
    font-size:13px;
    color:var(--text-muted);
    line-height:1.4;
  }
  .eyebrow{
    font-family:'IBM Plex Mono', monospace;
    font-size:14px;
    color:var(--accent-2);
    letter-spacing:0.02em;
    margin-bottom:10px;
  }
  h1{
    font-size:30px;
    font-weight:700;
    margin:0 0 10px;
    letter-spacing:-0.01em;
  }
  header p{
    color:var(--text-muted);
    font-size:16px;
    margin:0;
    max-width:520px;
  }

  /* 햄버거 메뉴 버튼 (좌상단 고정) */
  .menu-toggle{
    position:fixed;
    top:18px; left:18px;
    z-index:50;
    width:46px; height:46px;
    border-radius:10px;
    background:var(--panel);
    border:1.5px solid var(--panel-border);
    color:var(--text);
    font-size:20px;
    cursor:pointer;
    display:flex;
    align-items:center;
    justify-content:center;
    box-shadow:0 4px 14px rgba(0,0,0,0.35);
  }
  .menu-toggle:hover{ border-color:var(--accent-2); }

  /* 사이드바 뒤 어둡게 깔리는 배경 */
  .menu-overlay{
    position:fixed; inset:0;
    background:rgba(8,10,13,0.55);
    z-index:65;
    opacity:0;
    pointer-events:none;
    transition:opacity 0.2s ease;
  }
  .menu-overlay.active{ opacity:1; pointer-events:auto; }

  /* 사이드바: 화면 왼쪽에 붙어 슬라이드로 나타남 */
  .menu-panel{
    position:fixed;
    top:0; left:0;
    height:100vh;
    width:min(280px, 82vw);
    z-index:70;
    background:var(--panel);
    border-right:1.5px solid var(--panel-border);
    box-shadow:10px 0 30px rgba(0,0,0,0.4);
    padding:18px 10px;
    display:flex;
    flex-direction:column;
    overflow-y:auto;
    transform:translateX(-100%);
    transition:transform 0.25s ease;
  }
  .menu-panel.active{ transform:translateX(0); }

  .menu-header{
    display:flex;
    align-items:center;
    justify-content:space-between;
    padding:6px 10px 14px;
    margin-bottom:8px;
    border-bottom:1px solid var(--panel-border);
  }
  .menu-header .menu-title{
    font-size:13px;
    color:var(--text-muted);
    letter-spacing:0.02em;
  }
  .menu-close{
    background:none;
    border:none;
    color:var(--text-muted);
    font-size:19px;
    line-height:1;
    cursor:pointer;
    padding:4px 6px;
  }
  .menu-close:hover{ color:var(--text); }

  .menu-grid{
    display:flex;
    flex-direction:column;
    gap:2px;
  }
  .menu-category-label{
    font-family:'IBM Plex Mono', monospace;
    font-size:11px;
    font-weight:600;
    letter-spacing:0.06em;
    text-transform:uppercase;
    color:var(--text-muted);
    padding:16px 12px 6px;
  }
  .menu-category-label:first-child{ padding-top:6px; }
  .menu-item{
    appearance:none;
    -webkit-appearance:none;
    background:transparent;
    border:none;
    border-left:2px solid transparent;
    border-radius:8px;
    color:var(--text);
    text-decoration:none;
    box-sizing:border-box;
    font-family:'IBM Plex Sans KR', sans-serif;
    font-size:15px;
    font-weight:500;
    padding:11px 12px;
    cursor:pointer;
    text-align:left;
    line-height:1.3;
    display:flex;
    align-items:flex-start;
    gap:10px;
    width:100%;
  }
  .menu-item .dot{
    width:6px; height:6px;
    min-width:6px;
    margin-top:7px;
    border-radius:50%;
    background:var(--panel-border);
  }
  .menu-item .menu-item-text{ display:flex; flex-direction:column; gap:2px; }
  .menu-item .menu-item-desc{
    font-size:12px;
    font-weight:400;
    color:var(--text-muted);
  }
  .menu-item:hover{ background:var(--hover-bg); color:var(--accent-2); }
  .menu-item:hover .dot{ background:var(--accent-2); }
  .menu-item.is-current{
    background:var(--hover-bg);
    border-left-color:var(--accent);
  }
  .menu-item.is-current .dot{ background:var(--accent); }
  .menu-item.is-current .menu-item-text > span:first-child{ color:var(--accent); font-weight:600; }

  /* 사이드바 하단 설정 영역 (테마/언어) */
  .menu-footer{
    margin-top:auto;
    padding-top:14px;
    border-top:1px solid var(--panel-border);
  }
  .menu-section-label{
    font-size:12px;
    color:var(--text-muted);
    padding:0 12px;
    margin-bottom:8px;
    letter-spacing:0.02em;
  }
  .menu-section-label.spaced{ margin-top:16px; }
  .toggle-group{
    display:flex;
    gap:6px;
    padding:0 10px;
  }
  .toggle-btn{
    flex:1;
    appearance:none;
    -webkit-appearance:none;
    background:var(--sunken);
    border:1.5px solid var(--panel-border);
    color:var(--text-muted);
    font-family:'IBM Plex Sans KR', sans-serif;
    font-size:13.5px;
    font-weight:500;
    padding:9px 6px;
    border-radius:8px;
    cursor:pointer;
    text-align:center;
  }
  .toggle-btn:hover{ color:var(--text); }
  .toggle-btn.active{
    background:var(--accent-2);
    border-color:var(--accent-2);
    color:var(--bg);
    font-weight:600;
  }

  .module{
    background:transparent;
    border:none;
    border-top:3px solid var(--accent);
    border-radius:0;
    padding:36px 0 44px;
    margin:0;
    position:relative;
    scroll-margin-top:20px;
  }
  .module.teal{ border-top-color:var(--accent-2); }
  .module.rust{ border-top-color:var(--accent-3); }

  .module h1, .module h2{
    font-size:26px;
    font-weight:700;
    margin:18px 0 8px;
    letter-spacing:-0.01em;
  }
  .module .desc{
    color:var(--text-muted);
    font-size:15.5px;
    margin:0 0 22px;
  }

  .field-row{
    display:flex;
    flex-wrap:wrap;
    gap:14px;
    margin-bottom:16px;
  }
  .field{flex:1;min-width:130px;}
  .field label{
    display:block;
    font-size:14px;
    font-weight:500;
    color:var(--text-muted);
    margin-bottom:7px;
  }
  .field input, .field select{
    width:100%;
    background:var(--sunken);
    border:1.5px solid var(--panel-border);
    color:var(--text);
    font-family:'IBM Plex Mono', monospace;
    font-size:17px;
    padding:12px 14px;
    border-radius:8px;
    outline:none;
    min-height:48px;
  }
  .field input:focus, .field select:focus{
    border-color:var(--accent-2);
  }
  /* 키보드 포커스 표시 (접근성) */
  .field input:focus-visible, .field select:focus-visible,
  .menu-item:focus-visible, .menu-close:focus-visible, .menu-toggle:focus-visible,
  .toggle-btn:focus-visible{
    outline:2px solid var(--accent-2);
    outline-offset:2px;
  }
  .field.has-error input, .field.has-error select{
    border-color:var(--danger);
  }
  .field-error{
    display:none;
    align-items:center;
    gap:6px;
    font-size:13px;
    color:var(--danger);
    margin-top:6px;
  }
  .field.has-error .field-error{ display:flex; }

  .readout{
    position:relative;
    margin-top:20px;
    padding:18px 20px;
    background:var(--sunken);
    border-radius:10px;
    border:1px solid var(--panel-border);
  }
  .copy-btn{
    position:absolute;
    top:12px; right:12px;
    appearance:none;
    -webkit-appearance:none;
    background:var(--panel);
    border:1px solid var(--panel-border);
    color:var(--text-muted);
    font-family:'IBM Plex Sans KR', sans-serif;
    font-size:12px;
    font-weight:500;
    padding:6px 10px;
    border-radius:6px;
    cursor:pointer;
  }
  .copy-btn:hover{ color:var(--text); border-color:var(--accent-2); }
  .copy-btn.is-copied{ color:var(--accent-2); border-color:var(--accent-2); }
  .readout .label{
    font-size:13px;
    color:var(--text-muted);
    margin-bottom:8px;
    letter-spacing:0.03em;
    text-transform:uppercase;
  }
  /* 결과값 = 가장 중요한 정보이므로 Amber로 고정(색상에 의미 부여) */
  .readout .value{
    font-family:'IBM Plex Mono', monospace;
    font-size:40px;
    font-weight:700;
    color:var(--accent);
    line-height:1.15;
    letter-spacing:-0.01em;
  }
  /* 주의가 필요한 결과값(물리적 한계, 경고성 수치)은 Rust로 전환 */
  .readout .value.is-caution{ color:var(--danger); }
  .readout .sub{
    font-family:'IBM Plex Mono', monospace;
    font-size:13.5px;
    color:var(--accent-2); /* Teal = 보조 정보·계산 과정 */
    margin-top:8px;
  }
  .readout .plain{
    font-size:14.5px;
    color:var(--text-muted);
    margin-top:10px;
    line-height:1.55;
  }

  table{
    width:100%;
    border-collapse:collapse;
    margin-top:20px;
    font-family:'IBM Plex Mono', monospace;
    font-size:15px;
    display:block;
    overflow-x:auto;
    -webkit-overflow-scrolling:touch;
  }
  th, td{
    text-align:left;
    padding:10px 8px;
    border-bottom:1px solid var(--panel-border);
    white-space:nowrap;
  }
  th{
    color:var(--text-muted);
    font-weight:500;
    font-size:13px;
    font-family:'IBM Plex Sans KR', sans-serif;
  }
  td.val{ color:var(--accent-2); text-align:right; font-weight:600; }

  .chart-wrap{
    margin-top:20px;
    background:var(--sunken);
    border:1px solid var(--panel-border);
    border-radius:10px;
    padding:16px 12px 10px;
    overflow-x:auto;
  }
  .chart-wrap svg{ width:100%; height:auto; display:block; min-width:320px; }
  .chart-caption{
    font-size:12.5px;
    color:var(--text-muted);
    margin-top:8px;
    text-align:center;
  }

  /* 공식 영역: 기술 문서 느낌 (dashed 프로토타입 스타일 제거) */
  .formula-block{
    margin-top:20px;
    border-top:1px solid var(--panel-border);
    padding-top:16px;
  }
  .formula-eyebrow{
    font-family:'IBM Plex Mono', monospace;
    font-size:11px;
    font-weight:600;
    letter-spacing:0.08em;
    color:var(--text-muted);
    margin-bottom:8px;
  }
  .formula-text{
    font-family:'IBM Plex Mono', monospace;
    font-size:14px;
    color:var(--text);
    background:var(--sunken);
    border-left:3px solid var(--accent-2);
    border-radius:4px;
    padding:12px 14px;
    overflow-x:auto;
    white-space:pre;
  }
  .formula-note{
    font-size:13px;
    color:var(--text-muted);
    margin-top:8px;
    line-height:1.5;
  }

  .warn{
    margin-top:12px;
    font-size:14px;
    color:var(--danger);
  }

  footer{
    color:var(--text-muted);
    font-size:13px;
    text-align:center;
    margin-top:24px;
  }
  footer p{ margin:6px 0; }
  footer .footer-links a{ color:var(--text-muted); text-decoration:none; }
  footer .footer-links a:hover{ color:var(--accent-2); }

  /* 좁은 화면(360~390px) 대응: 여백/글자 크기 미세 조정, 결과값·공식이 잘리지 않도록 */
  @media (max-width: 400px){
    .wrap{ padding:80px 14px 70px; }
    h1{ font-size:24px; }
    .module h1, .module h2{ font-size:22px; }
    .readout .value{ font-size:32px; }
    .field-row{ gap:10px; }
    .field{ min-width:100%; }
    .formula-text{ font-size:12.5px; padding:10px 12px; }
  }