:root {
  --vht-guide-orange: rgb(243, 146, 0);
  --vht-guide-blue: rgb(15, 112, 183);
  --vht-guide-blue-dark: rgb(10, 78, 128);
  --vht-guide-text: #263746;
  --vht-guide-muted: #647585;
  --vht-guide-border: #dbe5ec;
  --vht-guide-surface: #f5f9fc;
  --vht-guide-white: #ffffff;
}

.vht-electric-boiler-guide,
.vht-electric-boiler-guide * {
  box-sizing: border-box;
}

.vht-electric-boiler-guide {
  width: 100%;
  max-width: 1180px;
  margin: 0 auto;
  color: var(--vht-guide-text);
  font-family: inherit;
  font-size: 16px;
  line-height: 1.7;
}

.vht-electric-boiler-guide h1,
.vht-electric-boiler-guide h2,
.vht-electric-boiler-guide h3 {
  margin-top: 0;
  color: #172d3e;
  line-height: 1.25;
}

.vht-electric-boiler-guide h1 {
  max-width: 900px;
  margin-bottom: 18px;
  font-size: clamp(30px, 4vw, 48px);
}

.vht-electric-boiler-guide h2 {
  margin-bottom: 16px;
  font-size: clamp(24px, 3vw, 32px);
}

.vht-electric-boiler-guide h3 {
  margin-bottom: 8px;
  font-size: 19px;
}

.vht-electric-boiler-guide p {
  margin: 0 0 16px;
}

.vht-electric-boiler-guide a {
  color: var(--vht-guide-blue);
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

.vht-electric-boiler-guide a:hover {
  color: var(--vht-guide-blue-dark);
}

.vht-electric-boiler-guide a:focus-visible,
.vht-electric-boiler-guide summary:focus-visible,
.vht-electric-boiler-guide [tabindex="0"]:focus-visible {
  outline: 3px solid rgba(243, 146, 0, 0.45);
  outline-offset: 3px;
}

.vht-electric-boiler-guide__hero {
  position: relative;
  overflow: hidden;
  padding: clamp(28px, 5vw, 58px);
  border: 1px solid rgba(15, 112, 183, 0.16);
  border-radius: 22px;
  background:
    radial-gradient(circle at 92% 12%, rgba(243, 146, 0, 0.2), transparent 28%),
    linear-gradient(135deg, #f5faff 0%, #ffffff 72%);
}

.vht-electric-boiler-guide__hero::after {
  position: absolute;
  right: -55px;
  bottom: -55px;
  width: 170px;
  height: 170px;
  border: 22px solid rgba(15, 112, 183, 0.08);
  border-radius: 50%;
  content: "";
}

.vht-electric-boiler-guide__eyebrow {
  margin-bottom: 10px !important;
  color: var(--vht-guide-orange);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.vht-electric-boiler-guide__lead {
  position: relative;
  z-index: 1;
  max-width: 920px;
  margin-bottom: 0 !important;
  color: #405666;
  font-size: 18px;
}

.vht-electric-boiler-guide__toc {
  margin: 28px 0;
  padding: 22px 26px;
  border-left: 5px solid var(--vht-guide-blue);
  border-radius: 0 14px 14px 0;
  background: var(--vht-guide-surface);
}

.vht-electric-boiler-guide__toc strong {
  display: block;
  margin-bottom: 8px;
  color: var(--vht-guide-blue-dark);
  font-size: 18px;
}

.vht-electric-boiler-guide__toc ol {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 5px 32px;
  margin: 0;
  padding-left: 22px;
}

.vht-electric-boiler-guide__section {
  padding: clamp(28px, 5vw, 48px) 0;
  border-bottom: 1px solid var(--vht-guide-border);
  scroll-margin-top: 110px;
}

.vht-electric-boiler-guide__notice,
.vht-electric-boiler-guide__warning {
  padding: 24px 26px;
  border-radius: 15px;
}

.vht-electric-boiler-guide__notice {
  border: 1px solid rgba(15, 112, 183, 0.24);
  background: rgba(15, 112, 183, 0.07);
}

.vht-electric-boiler-guide__notice h2 {
  color: var(--vht-guide-blue-dark);
}

.vht-electric-boiler-guide__notice p,
.vht-electric-boiler-guide__warning p {
  margin-bottom: 0;
}

.vht-electric-boiler-guide__formula {
  margin: 22px 0;
  padding: 18px 24px;
  border-left: 5px solid var(--vht-guide-orange);
  border-radius: 0 12px 12px 0;
  background: #fff8ed;
  color: #6c4300;
  font-size: clamp(21px, 3vw, 28px);
  font-weight: 700;
  text-align: center;
}

.vht-electric-boiler-guide__formula--example {
  border-left-color: var(--vht-guide-blue);
  background: var(--vht-guide-surface);
  color: var(--vht-guide-blue-dark);
  font-size: clamp(18px, 2.5vw, 24px);
}

.vht-electric-boiler-guide__definitions {
  margin: 0 0 28px;
  padding-left: 23px;
}

.vht-electric-boiler-guide__definitions li + li {
  margin-top: 5px;
}

.vht-electric-boiler-guide__cards {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 18px;
  margin: 24px 0 34px;
}

.vht-electric-boiler-guide__card {
  padding: 22px;
  border: 1px solid var(--vht-guide-border);
  border-top: 4px solid var(--vht-guide-blue);
  border-radius: 13px;
  background: var(--vht-guide-white);
  box-shadow: 0 7px 22px rgba(18, 54, 78, 0.07);
}

.vht-electric-boiler-guide__card:nth-child(2) {
  border-top-color: var(--vht-guide-orange);
}

.vht-electric-boiler-guide__card:nth-child(4) {
  border-top-color: var(--vht-guide-orange);
}

.vht-electric-boiler-guide__card p:last-child {
  margin-bottom: 0;
  color: var(--vht-guide-muted);
}

.vht-electric-boiler-guide__table-wrap {
  width: 100%;
  margin: 22px 0 12px;
  overflow-x: auto;
  border: 1px solid var(--vht-guide-border);
  border-radius: 14px;
  background: var(--vht-guide-white);
  -webkit-overflow-scrolling: touch;
}

.vht-electric-boiler-guide__table {
  width: 100%;
  min-width: 720px;
  margin: 0;
  border: 0;
  border-collapse: collapse;
  background: var(--vht-guide-white);
}

.vht-electric-boiler-guide__table th,
.vht-electric-boiler-guide__table td {
  padding: 14px 16px;
  border: 0;
  border-bottom: 1px solid var(--vht-guide-border);
  text-align: left;
  vertical-align: middle;
}

.vht-electric-boiler-guide__table th {
  background: var(--vht-guide-blue);
  color: var(--vht-guide-white);
  font-weight: 700;
}

.vht-electric-boiler-guide__table tbody tr:nth-child(even) {
  background: #f8fbfd;
}

.vht-electric-boiler-guide__table tbody tr:last-child td {
  border-bottom: 0;
}

.vht-electric-boiler-guide__table td:nth-child(2) {
  color: var(--vht-guide-blue-dark);
  font-weight: 700;
  white-space: nowrap;
}

.vht-electric-boiler-guide__table--compact {
  min-width: 620px;
}

.vht-electric-boiler-guide__caption {
  margin-top: 12px !important;
  color: var(--vht-guide-muted);
  font-size: 14px;
}

.vht-electric-boiler-guide__checklist {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

.vht-electric-boiler-guide__checklist > div {
  position: relative;
  padding: 20px 20px 20px 54px;
  border: 1px solid var(--vht-guide-border);
  border-radius: 12px;
  background: var(--vht-guide-white);
}

.vht-electric-boiler-guide__checklist > div::before {
  position: absolute;
  top: 21px;
  left: 20px;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--vht-guide-orange);
  color: var(--vht-guide-white);
  content: "\2713";
  font-size: 14px;
  font-weight: 700;
  line-height: 22px;
  text-align: center;
}

.vht-electric-boiler-guide__checklist p {
  margin-bottom: 0;
  color: var(--vht-guide-muted);
}

.vht-electric-boiler-guide__warning {
  margin-top: 24px;
  border: 1px solid rgba(243, 146, 0, 0.35);
  border-left: 5px solid var(--vht-guide-orange);
  background: #fff8ed;
}

.vht-electric-boiler-guide__warning h3 {
  color: #754900;
}

.vht-electric-boiler-guide__steps {
  margin: 0;
  padding: 0;
  counter-reset: vht-guide-step;
  list-style: none;
}

.vht-electric-boiler-guide__steps li {
  position: relative;
  min-height: 54px;
  padding: 0 0 24px 68px;
  counter-increment: vht-guide-step;
}

.vht-electric-boiler-guide__steps li::before {
  position: absolute;
  top: 0;
  left: 0;
  display: grid;
  width: 44px;
  height: 44px;
  border-radius: 12px;
  background: var(--vht-guide-blue);
  color: var(--vht-guide-white);
  content: counter(vht-guide-step);
  font-weight: 700;
  place-items: center;
}

.vht-electric-boiler-guide__steps li::after {
  position: absolute;
  top: 48px;
  bottom: 4px;
  left: 21px;
  width: 2px;
  background: var(--vht-guide-border);
  content: "";
}

.vht-electric-boiler-guide__steps li:last-child::after {
  display: none;
}

.vht-electric-boiler-guide__steps strong,
.vht-electric-boiler-guide__steps span {
  display: block;
}

.vht-electric-boiler-guide__steps strong {
  margin-bottom: 4px;
  color: #172d3e;
  font-size: 18px;
}

.vht-electric-boiler-guide__steps span {
  color: var(--vht-guide-muted);
}

.vht-electric-boiler-guide__faq {
  display: grid;
  gap: 12px;
}

.vht-electric-boiler-guide__faq details {
  overflow: hidden;
  border: 1px solid var(--vht-guide-border);
  border-radius: 12px;
  background: var(--vht-guide-white);
}

.vht-electric-boiler-guide__faq details[open] {
  border-color: rgba(15, 112, 183, 0.35);
  box-shadow: 0 6px 18px rgba(18, 54, 78, 0.06);
}

.vht-electric-boiler-guide__faq summary {
  position: relative;
  padding: 17px 52px 17px 20px;
  color: #172d3e;
  cursor: pointer;
  font-weight: 700;
  list-style: none;
}

.vht-electric-boiler-guide__faq summary::-webkit-details-marker {
  display: none;
}

.vht-electric-boiler-guide__faq summary::after {
  position: absolute;
  top: 50%;
  right: 20px;
  color: var(--vht-guide-blue);
  content: "+";
  font-size: 25px;
  line-height: 1;
  transform: translateY(-50%);
}

.vht-electric-boiler-guide__faq details[open] summary::after {
  content: "\2212";
}

.vht-electric-boiler-guide__faq details p {
  margin: 0;
  padding: 0 20px 18px;
  color: var(--vht-guide-muted);
}

.vht-electric-boiler-guide__cta {
  display: grid;
  grid-template-columns: minmax(0, 1.5fr) minmax(280px, 0.75fr);
  gap: 30px;
  align-items: center;
  margin-top: 42px;
  padding: clamp(28px, 5vw, 46px);
  border-radius: 20px;
  background: var(--vht-guide-blue);
  color: var(--vht-guide-white);
}

.vht-electric-boiler-guide__cta h2 {
  margin-bottom: 10px;
  color: var(--vht-guide-white);
}

.vht-electric-boiler-guide__cta p {
  margin-bottom: 0;
  color: rgba(255, 255, 255, 0.88);
}

.vht-electric-boiler-guide__actions {
  display: grid;
  gap: 11px;
}

.vht-electric-boiler-guide__button {
  display: inline-flex;
  min-height: 46px;
  align-items: center;
  justify-content: center;
  padding: 11px 18px;
  border: 2px solid transparent;
  border-radius: 9px;
  font-weight: 700;
  line-height: 1.3;
  text-align: center;
  text-decoration: none !important;
  transition: background-color 0.2s ease, border-color 0.2s ease, color 0.2s ease;
}

.vht-electric-boiler-guide__button--primary {
  background: var(--vht-guide-orange);
  color: #172d3e !important;
}

.vht-electric-boiler-guide__button--primary:hover {
  background: #ffad2f;
}

.vht-electric-boiler-guide__button--secondary {
  border-color: rgba(255, 255, 255, 0.75);
  color: var(--vht-guide-white) !important;
}

.vht-electric-boiler-guide__button--secondary:hover {
  border-color: var(--vht-guide-white);
  background: var(--vht-guide-white);
  color: var(--vht-guide-blue-dark) !important;
}

.vht-electric-boiler-guide__text-link {
  color: var(--vht-guide-white) !important;
  text-align: center;
}

@media (max-width: 1024px) {
  .vht-electric-boiler-guide__cards {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 767px) {
  .vht-electric-boiler-guide {
    font-size: 15px;
    line-height: 1.65;
  }

  .vht-electric-boiler-guide__hero {
    padding: 26px 20px;
    border-radius: 16px;
  }

  .vht-electric-boiler-guide__lead {
    font-size: 16px;
  }

  .vht-electric-boiler-guide__toc {
    padding: 18px 20px;
  }

  .vht-electric-boiler-guide__toc ol,
  .vht-electric-boiler-guide__cards,
  .vht-electric-boiler-guide__checklist,
  .vht-electric-boiler-guide__cta {
    grid-template-columns: 1fr;
  }

  .vht-electric-boiler-guide__section {
    padding: 32px 0;
  }

  .vht-electric-boiler-guide__notice,
  .vht-electric-boiler-guide__warning {
    padding: 20px;
  }

  .vht-electric-boiler-guide__formula {
    padding: 16px 14px;
  }

  .vht-electric-boiler-guide__checklist > div {
    padding: 18px 18px 18px 50px;
  }

  .vht-electric-boiler-guide__checklist > div::before {
    top: 19px;
    left: 16px;
  }

  .vht-electric-boiler-guide__steps li {
    padding-left: 58px;
  }

  .vht-electric-boiler-guide__cta {
    margin-top: 30px;
    padding: 26px 20px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .vht-electric-boiler-guide__button {
    transition: none;
  }
}