:root {
  --bg: #ffffff;
  --text: #101010;
  --muted: #4b4b4b;
  --line: #d5d5d5;
  --panel: #f7f7f7;
  --primary: #0b3a8f;
  --primary-hover: #082f73;
  --danger: #b61f1f;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: Arial, Helvetica, sans-serif;
  line-height: 1.5;
}

a {
  color: var(--primary);
}

a:focus-visible,
button:focus-visible,
input:focus-visible,
summary:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.container {
  width: min(960px, 92%);
  margin: 0 auto;
}

.site-header {
  border-bottom: 1px solid var(--line);
  background: #ffffff;
}

.header-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  padding: 0.9rem 0;
}

.logo {
  color: var(--text);
  text-decoration: none;
  font-size: 1.1rem;
  font-weight: 700;
}

.header-nav,
.footer-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  list-style: none;
  margin: 0;
  padding: 0;
}

.header-nav a,
.footer-nav a {
  color: var(--text);
  text-decoration: none;
}

.hero {
  padding: 1.8rem 0 1rem;
}

.hero h1 {
  margin: 0;
  font-size: clamp(1.9rem, 3vw, 2.4rem);
  line-height: 1.2;
}

.hero-subtitle {
  margin: 0.6rem 0 0;
  color: var(--muted);
}

.calculator-wrap {
  margin-bottom: 1.4rem;
}

.calculator-panel {
  border: 1px solid var(--line);
  background: var(--panel);
  padding: 1rem;
}

#dph-form {
  display: grid;
  gap: 0.95rem;
}

.field-block label {
  display: block;
  font-weight: 700;
  margin-bottom: 0.35rem;
}

.field-block input {
  width: 100%;
  border: 1px solid var(--line);
  background: #ffffff;
  color: var(--text);
  font-size: 1rem;
  padding: 0.65rem 0.7rem;
}

.option-fieldset {
  border: 1px solid var(--line);
  padding: 0.7rem;
  margin: 0;
  display: grid;
  gap: 0.5rem;
}

.option-fieldset legend {
  font-weight: 700;
  padding: 0 0.35rem;
}

.option-fieldset label {
  display: inline-flex;
  align-items: center;
  gap: 0.42rem;
  font-size: 0.98rem;
}

.button-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem;
}

.primary-btn,
.secondary-btn {
  border: 1px solid var(--line);
  cursor: pointer;
  font-size: 1rem;
  font-weight: 700;
  padding: 0.75rem 1rem;
}

.primary-btn {
  background: var(--primary);
  border-color: var(--primary);
  color: #ffffff;
}

.primary-btn:hover,
.primary-btn:focus-visible {
  background: var(--primary-hover);
}

.secondary-btn {
  background: #ffffff;
  color: var(--text);
}

.form-message {
  margin: 0;
  min-height: 1.5rem;
  color: #1d5a1f;
  font-size: 0.95rem;
}

.form-message.error {
  color: var(--danger);
}

.results {
  margin-top: 1rem;
  border-top: 1px solid var(--line);
  padding-top: 1rem;
}

.results h3 {
  margin: 0 0 0.6rem;
  font-size: 1.2rem;
}

.result-item {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 1rem;
  border: 1px solid var(--line);
  background: #ffffff;
  padding: 0.65rem 0.75rem;
  margin-bottom: 0.55rem;
}

.result-label,
.result-value {
  margin: 0;
}

.result-label {
  font-weight: 700;
}

.result-value {
  font-size: clamp(1.05rem, 2vw, 1.35rem);
}

.content-section {
  margin-bottom: 1.9rem;
}

.content-section h2 {
  margin: 0 0 0.6rem;
  font-size: 1.4rem;
}

.official-source {
  border-left: 3px solid var(--primary);
  padding-left: 0.8rem;
  margin-top: 0.8rem;
}

.official-source p {
  margin: 0;
}

details {
  border: 1px solid var(--line);
  background: #ffffff;
  padding: 0.65rem;
  margin-bottom: 0.65rem;
}

summary {
  cursor: pointer;
  font-weight: 700;
}

.site-footer {
  border-top: 1px solid var(--line);
  margin-top: 2.2rem;
  padding: 1rem 0;
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
}

.footer-inner p {
  margin: 0;
  color: var(--muted);
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (max-width: 680px) {
  .header-inner {
    flex-wrap: wrap;
  }

  .button-row {
    flex-direction: column;
  }

  .button-row button {
    width: 100%;
  }

  .result-item {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.3rem;
  }
}