html, body { margin: 0; min-height: 100%; }

.calcpage {
  box-sizing: border-box;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.calcpage__head {
  box-sizing: border-box;
  max-width: 1180px;
  width: 100%;
  margin: 0 auto;
  padding: 14px 20px 8px;
  
  font: 15px/1.45 Inter, -apple-system, "Segoe UI", Roboto, Arial, sans-serif;
  color: #1b1b1b;
}

.calcpage__back {
  display: inline-block;
  margin-bottom: 6px;
  font-size: 13px;
  color: #2f3336;
  text-decoration: none;
  border-bottom: 1px solid #d9dbde;
}

.calcpage__back:hover { border-bottom-color: #2f3336; }

.calcpage__title { margin: 0 0 6px; font-size: 24px; line-height: 1.2; }

.calcpage__intro { margin: 0; color: #63676c; }

.calcpage__frame {
  display: block;
  width: 100%;
  min-height: 620px;
  border: 0;
}

@media (max-width: 600px) {
  .calcpage__head { padding: 10px 12px 6px; font-size: 13px; }
  .calcpage__title { font-size: 18px; }
  .calcpage__frame { min-height: 520px; }
}