@layer km-base {
  * {
    box-sizing: border-box;
  }

  body {
    margin: 0;
    font-family: -apple-system,BlinkMacSystemFont,"Noto Sans JP",sans-serif;
    background: var(--km-color-page);
    color: var(--km-color-body);
    font-size: var(--km-font-body);
    line-height: 1.75;
    font-weight: var(--km-weight-regular);
    -webkit-font-smoothing: antialiased;
  }

  /* Signed-in pages scroll inside a dedicated viewport container.
     This keeps the content width stable when the vertical scrollbar appears,
     while the fixed bottom navigation remains outside the scroll gutter. */
  .km-app-scroll {
    height: 100vh;
    height: 100dvh;
    overflow-x: hidden;
    overflow-y: auto;
  }

  body.auth-signed-in {
    overflow: hidden;
  }

  body.modal-open .km-app-scroll {
    overflow-y: hidden;
  }

  @media (min-width: 601px) {
    .km-app-scroll {
      scrollbar-gutter: stable both-edges;
    }
  }

  .app {
    max-width: var(--km-app-max-width);
    margin: auto;
    padding-bottom: var(--km-layout-bottom-nav-reserve);
  }

  .header {
    padding: var(--km-space-md);
  }

  .header h1 {
    margin: 0;
    font-size: var(--km-font-page);
    line-height: 1.4;
    font-weight: var(--km-weight-semibold);
    color: var(--km-color-title);
  }

  .header p {
    margin: var(--km-space-xs) 0 0;
    color: var(--km-color-muted);
    font-size: var(--km-font-meta);
    line-height: 1.6;
  }

  main {
    padding: 0 var(--km-space-md);
  }
}