:root{
    --bg-deep: #16221C;
    --bg-panel: #1E2E26;
    --wood-dark: #34211A;
    --brass: #B8935A;
    --brass-light: #D9BD8A;
    --paper: #EFE6D8;
    --paper-dim: #C9BFAF;
    --ink: #2B1B12;
    --seal-red: #A5352E;
    --font-display: "Hiragino Mincho ProN", "Yu Mincho", "YuMincho", serif;
    --font-body: "Hiragino Kaku Gothic ProN", "Yu Gothic", "YuGothic", sans-serif;
  }

  * { box-sizing: border-box; }

  html, body {
    margin: 0;
    padding: 0;
    background: var(--bg-deep);
    color: var(--paper);
    font-family: var(--font-body);
  }

  body { min-height: 100vh; display: flex; flex-direction: column; }

  header {
    padding: 40px 24px 24px;
    text-align: center;
    border-bottom: 1px solid rgba(184,147,90,0.25);
  }

  .logo {
    font-family: var(--font-display);
    font-size: clamp(26px, 5vw, 38px);
    font-weight: 700;
    letter-spacing: 0.06em;
    margin: 0;
  }

  .logo span { color: var(--brass-light); }

  .tagline {
    margin: 10px 0 0;
    font-size: 14px;
    color: var(--paper-dim);
  }

  main {
    flex: 1;
    display: grid;
    grid-template-columns: 320px 1fr;
    max-width: 1100px;
    width: 100%;
    margin: 0 auto;
  }

  @media (max-width: 800px) {
    main { grid-template-columns: 1fr; }
  }

  .form-panel {
    padding: 24px;
    border-right: 1px solid rgba(184,147,90,0.2);
  }

  @media (max-width: 800px) {
    .form-panel { border-right: none; border-bottom: 1px solid rgba(184,147,90,0.2); }
  }

  .field { margin-bottom: 20px; }

  .field label {
    display: block;
    font-size: 12px;
    color: var(--paper-dim);
    margin-bottom: 6px;
    letter-spacing: 0.03em;
  }

  .field input {
    width: 100%;
    background: rgba(239,230,216,0.06);
    border: 1px solid rgba(184,147,90,0.35);
    border-radius: 4px;
    padding: 10px 12px;
    color: var(--paper);
    font-size: 14px;
    font-family: var(--font-body);
  }

  .field input:focus {
    outline: none;
    border-color: var(--brass-light);
  }

  .field .hint {
    font-size: 11px;
    color: var(--paper-dim);
    opacity: 0.7;
    margin-top: 4px;
  }

  .style-tabs {
    display: flex;
    gap: 6px;
    margin-top: 4px;
  }

  .style-tab {
    flex: 1;
    background: transparent;
    border: 1px solid rgba(184,147,90,0.35);
    color: var(--paper-dim);
    font-family: var(--font-body);
    font-size: 13px;
    padding: 10px 4px;
    border-radius: 3px;
    cursor: pointer;
  }

  .style-tab.active {
    background: var(--brass);
    border-color: var(--brass);
    color: var(--wood-dark);
    font-weight: 700;
  }

  .preview-panel {
    padding: 24px;
    display: flex;
    flex-direction: column;
    align-items: center;
  }

  #cert-wrap {
    width: 100%;
    max-width: 720px;
    background: var(--bg-panel);
    border-radius: 8px;
    padding: 20px;
    box-shadow: inset 0 0 40px rgba(0,0,0,0.3);
  }

  #cert { width: 100%; height: auto; display: block; }

  .controls {
    margin-top: 20px;
    display: flex;
    justify-content: flex-end;
    gap: 10px;
    width: 100%;
    max-width: 720px;
  }

  #save-btn {
    background: var(--brass);
    color: var(--wood-dark);
    border: none;
    font-family: var(--font-body);
    font-weight: 700;
    font-size: 14px;
    padding: 12px 24px;
    border-radius: 4px;
    cursor: pointer;
  }

  #save-btn:hover { filter: brightness(1.1); }

  #copy-url-btn {
    background: transparent;
    color: var(--paper);
    border: 1px solid rgba(184,147,90,0.5);
    font-family: var(--font-body);
    font-weight: 700;
    font-size: 14px;
    padding: 12px 20px;
    border-radius: 4px;
    cursor: pointer;
  }

  #copy-url-btn:hover { border-color: var(--brass-light); }

  footer {
    text-align: center;
    padding: 20px;
    font-size: 12px;
    color: var(--paper-dim);
    opacity: 0.6;
  }