:root {
  --bg: #F5F6F7;
  --ink: #2e3848;
  --accent: #74fbfb;
  --link: #4eaff8;
  --line: #d2d2d7;
  --err: #a01717;
}
* { box-sizing: border-box; }
html, body { height: 100%; margin: 0; }
body {
  font-family: 'Lato', system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
  background: var(--bg); color: var(--ink);
}

/* ---- Login ---- */
body.login { display: grid; place-items: center; padding: 24px; }
body.login main {
  background: white; border: 1px solid var(--line); border-radius: 16px;
  padding: 32px 28px; width: 100%; max-width: 380px;
}
body.login h1 { margin: 0 0 4px; font-weight: 900; font-size: 28px; }
body.login .sub { margin: 0 0 24px; color: #666; font-size: 14px; }
body.login label { display: block; font-size: 13px; font-weight: 700; margin-bottom: 14px; }
body.login label small { font-weight: 400; color: #888; }
body.login input {
  display: block; width: 100%; margin-top: 6px; padding: 10px 12px;
  border: 1px solid var(--line); border-radius: 8px; font-size: 15px;
  font-family: inherit;
}
body.login input:focus { outline: 2px solid var(--accent); border-color: transparent; }
body.login button {
  display: block; width: 100%; margin-top: 8px; padding: 12px;
  background: var(--ink); color: var(--accent); border: 0; border-radius: 8px;
  font-weight: 700; font-size: 15px; cursor: pointer;
}
body.login .err {
  background: #fde7e7; color: var(--err); padding: 10px 12px; border-radius: 8px;
  margin-bottom: 16px; font-size: 14px;
}

/* ---- Viewer ---- */
body.viewer { display: flex; flex-direction: column; overflow: hidden; }
body.viewer header {
  display: flex; align-items: center; justify-content: space-between;
  background: var(--ink); color: white; padding: 12px 20px;
}
body.viewer header h1 { font-size: 18px; font-weight: 900; margin: 0; }
body.viewer .logout {
  color: var(--accent); text-decoration: none; font-size: 13px; font-weight: 700;
}
body.viewer .tabs {
  display: flex; gap: 4px; overflow-x: auto; background: white;
  border-bottom: 1px solid var(--line); padding: 0 12px;
}
body.viewer .tabs::-webkit-scrollbar { height: 4px; }
body.viewer .tab {
  flex: 0 0 auto; padding: 10px 14px; background: transparent; border: 0;
  border-bottom: 3px solid transparent; color: #555; font-weight: 700;
  font-size: 13px; cursor: pointer; white-space: nowrap; font-family: inherit;
}
body.viewer .tab:hover { color: var(--ink); }
body.viewer .tab.active { color: var(--ink); border-bottom-color: var(--link); }
body.viewer #frame {
  flex: 1; width: 100%; border: 0; background: white;
}
body.viewer .empty {
  margin: 60px auto; padding: 24px 28px; background: white;
  border: 1px dashed var(--line); border-radius: 12px; max-width: 600px;
  text-align: center; color: #555;
}