/* =============================================
   Calcak – Design System & Layout
   Breakpoints: 375 / 768 / 1024 / 1280
   ============================================= */

/* ---- Reset & Base ---- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  /* Brand Colors */
  --color-primary:     #2563EB;
  --color-primary-dk:  #1D4ED8;
  --color-accent:      #F59E0B;
  --color-accent-dk:   #D97706;

  /* Neutrals */
  --color-bg:          #F8FAFC;
  --color-surface:     #FFFFFF;
  --color-border:      #E2E8F0;
  --color-text:        #0F172A;
  --color-text-muted:  #64748B;

  /* Calculator Keys */
  --key-num-bg:        #1E293B;
  --key-num-hover:     #334155;
  --key-fn-bg:         #475569;
  --key-fn-hover:      #64748B;
  --key-op-bg:         #2563EB;
  --key-op-hover:      #1D4ED8;
  --key-eq-bg:         #F59E0B;
  --key-eq-hover:      #D97706;
  --key-text:          #FFFFFF;

  /* Typography */
  --font-base:         'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --text-xs:           0.75rem;
  --text-sm:           0.875rem;
  --text-base:         1rem;
  --text-lg:           1.125rem;
  --text-xl:           1.25rem;
  --text-2xl:          1.5rem;
  --text-3xl:          1.875rem;
  --text-4xl:          2.25rem;

  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;

  /* Radius */
  --radius-sm:  6px;
  --radius-md:  12px;
  --radius-lg:  16px;
  --radius-xl:  24px;
  --radius-full: 9999px;

  /* Shadow */
  --shadow-sm:  0 1px 3px rgba(0,0,0,.08);
  --shadow-md:  0 4px 16px rgba(0,0,0,.10);
  --shadow-lg:  0 8px 32px rgba(0,0,0,.12);

  /* Layout */
  --header-h:   64px;
  --container:  1280px;
}

html { font-size: 16px; scroll-behavior: smooth; }

body {
  font-family: var(--font-base);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--color-primary); text-decoration: none; }
a:hover { text-decoration: underline; }
ul { list-style: none; }

/* Accessibility */
.sr-only {
  position: absolute; width: 1px; height: 1px;
  padding: 0; margin: -1px; overflow: hidden;
  clip: rect(0,0,0,0); white-space: nowrap; border: 0;
}
:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* ---- Container ---- */
.container {
  width: 100%;
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 var(--space-4);
}

/* =============================================
   HEADER
   ============================================= */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-h);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  box-shadow: var(--shadow-sm);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
  gap: var(--space-6);
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-text);
  text-decoration: none;
  white-space: nowrap;
}
.logo-icon { font-size: 1.4rem; color: var(--color-primary); }
.logo-text { color: var(--color-primary); }

.main-nav ul {
  display: flex;
  gap: var(--space-1);
  list-style: none;
  margin: 0; padding: 0;
}
.main-nav a {
  display: block;
  padding: var(--space-2) var(--space-3);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-muted);
  border-radius: var(--radius-sm);
  transition: color .15s, background .15s;
}
.main-nav a:hover,
.main-nav a.active {
  color: var(--color-primary);
  background: #EFF6FF;
  text-decoration: none;
}

/* ---- Dropdown ---- */
.main-nav .has-dropdown {
  position: relative;
}
.main-nav .dropdown {
  display: none;
  position: absolute;
  top: calc(100% + 4px);
  left: 0;
  min-width: 160px;
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: 0 4px 16px rgba(0,0,0,.1);
  z-index: 200;
  flex-direction: column;
  gap: 0;
  padding: var(--space-1) 0;
}
.main-nav .has-dropdown:hover .dropdown,
.main-nav .has-dropdown.open .dropdown {
  display: flex;
}
.main-nav .dropdown li { list-style: none; }
.main-nav .dropdown a {
  border-radius: 0;
  padding: var(--space-2) var(--space-3);
  white-space: nowrap;
}


.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-2);
}
.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: .2s;
}

/* =============================================
   AD BANNERS
   ============================================= */
.ad-banner {
  display: flex;
  justify-content: center;
  align-items: center;
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
  border-bottom: 1px solid var(--color-border);
  padding: var(--space-2) 0;
}
.ad-placeholder {
  display: flex;
  align-items: center;
  justify-content: center;
  background: #F1F5F9;
  border: 1px dashed #CBD5E1;
  border-radius: var(--radius-sm);
  color: var(--color-text-muted);
  font-size: var(--text-xs);
  font-weight: 500;
  letter-spacing: .05em;
  text-transform: uppercase;
}
.ad-top .ad-placeholder,
.ad-bottom .ad-placeholder { width: 728px; height: 90px; }
.ad-sidebar { width: 100%; border-radius: var(--radius-md); overflow: hidden; }
.ad-300x250 { height: 250px; }
.ad-300x600 { height: 600px; }

/* =============================================
   MAIN 3-COLUMN LAYOUT
   ============================================= */
.main-layout {
  display: grid;
  grid-template-columns: 200px 1fr 300px;
  gap: var(--space-6);
  padding-top: var(--space-6);
  padding-bottom: var(--space-8);
  align-items: start;
}

/* =============================================
   LEFT SIDEBAR
   ============================================= */
.sidebar-left {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  position: sticky;
  top: calc(var(--header-h) + var(--space-4));
}

.sidebar-title {
  font-size: var(--text-sm);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: var(--color-text-muted);
  margin-bottom: var(--space-3);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.category-list { display: flex; flex-direction: column; gap: var(--space-1); }
.cat-item {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-muted);
  transition: background .15s, color .15s;
}
.cat-item:hover,
.cat-item.active {
  background: #EFF6FF;
  color: var(--color-primary);
  text-decoration: none;
}
.cat-icon { font-size: 1rem; width: 20px; text-align: center; }

/* =============================================
   CENTER: CALCULATOR
   ============================================= */
.calc-main {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
  min-width: 0;
}

.breadcrumb ol {
  display: flex;
  gap: var(--space-2);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  align-items: center;
}
.breadcrumb li + li::before { content: '/'; margin-right: var(--space-2); }
.breadcrumb a { color: var(--color-text-muted); }
.breadcrumb a:hover { color: var(--color-primary); }

.calc-card {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  padding: var(--space-6);
  max-width: 420px;
  margin: 0 auto;
  width: 100%;
}

.calc-title {
  font-size: var(--text-xl);
  font-weight: 700;
  margin-bottom: var(--space-4);
  color: var(--color-text);
}

/* Display */
.calc-display {
  background: var(--key-num-bg);
  border-radius: var(--radius-md);
  padding: var(--space-4) var(--space-5);
  margin-bottom: var(--space-4);
  text-align: right;
  min-height: 90px;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
}
.calc-expression {
  font-size: var(--text-sm);
  color: #94A3B8;
  min-height: 1.4em;
  word-break: break-all;
}
.calc-result {
  font-size: var(--text-4xl);
  font-weight: 300;
  color: #FFFFFF;
  word-break: break-all;
  line-height: 1.2;
}

/* Keypad */
.calc-keypad {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-2);
}

.btn {
  border: none;
  border-radius: var(--radius-md);
  font-family: var(--font-base);
  font-size: var(--text-xl);
  font-weight: 500;
  cursor: pointer;
  padding: 0;
  height: 72px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: filter .1s, transform .08s;
  color: var(--key-text);
  -webkit-tap-highlight-color: transparent;
}
.btn:active { transform: scale(.94); filter: brightness(.85); }

.btn-num  { background: var(--key-num-bg); }
.btn-num:hover  { background: var(--key-num-hover); }
.btn-fn   { background: var(--key-fn-bg); }
.btn-fn:hover   { background: var(--key-fn-hover); }
.btn-op   { background: var(--key-op-bg); }
.btn-op:hover   { background: var(--key-op-hover); }
.btn-eq   { background: var(--key-eq-bg); color: #1E293B; font-weight: 700; }
.btn-eq:hover   { background: var(--key-eq-hover); }
.btn-zero { grid-column: span 2; justify-content: flex-start; padding-left: var(--space-6); }

/* History */
.calc-history {
  margin-top: var(--space-5);
  border-top: 1px solid var(--color-border);
  padding-top: var(--space-4);
}
.calc-history h3 {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text-muted);
  margin-bottom: var(--space-3);
  text-transform: uppercase;
  letter-spacing: .06em;
}
.history-list { display: flex; flex-direction: column; gap: var(--space-2); }
.history-list li {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  padding: var(--space-2) var(--space-3);
  background: var(--color-bg);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: background .15s;
}
.history-list li:hover { background: #EFF6FF; color: var(--color-primary); }
.history-empty { font-style: italic; background: none !important; cursor: default !important; }
.btn-clear-history {
  margin-top: var(--space-3);
  background: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: var(--space-1) var(--space-3);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  cursor: pointer;
  transition: border-color .15s, color .15s;
}
.btn-clear-history:hover { border-color: var(--color-primary); color: var(--color-primary); }

/* ---- Inline Calculator Disclaimer ---- */
.calc-disclaimer {
  margin-top: var(--space-4);
  padding: var(--space-3) var(--space-4);
  background: #FFFBEB;
  border: 1px solid #FDE68A;
  border-radius: var(--radius-sm);
  font-size: var(--text-xs);
  color: #92400E;
  line-height: 1.6;
}
.calc-disclaimer a {
  color: #92400E;
  font-weight: 600;
  text-decoration: underline;
}
.calc-disclaimer a:hover { color: var(--color-primary); }

/* ---- Footer Disclaimer Block ---- */
.footer-disclaimer {
  background: #1a2332;
  border-top: 1px solid #334155;
  padding: var(--space-5) 0;
}
.footer-disclaimer p {
  font-size: var(--text-xs);
  color: #64748B;
  line-height: 1.7;
  max-width: 900px;
}
.footer-bottom a {
  color: #64748B;
  text-decoration: underline;
}
.footer-bottom a:hover { color: #94A3B8; }

/* ---- Legal Pages (disclaimer.html, terms.html, privacy.html) ---- */
.legal-page { max-width: 800px; margin: var(--space-10) auto; padding: 0 var(--space-4) var(--space-12); }
.legal-page h1 { font-size: var(--text-3xl); font-weight: 700; margin-bottom: var(--space-2); }
.legal-page .legal-meta { font-size: var(--text-sm); color: var(--color-text-muted); margin-bottom: var(--space-8); }
.legal-page h2 { font-size: var(--text-xl); font-weight: 600; margin: var(--space-8) 0 var(--space-3); }
.legal-page p, .legal-page li {
  font-size: var(--text-base);
  color: var(--color-text-muted);
  line-height: 1.8;
  margin-bottom: var(--space-3);
}
.legal-page ul { list-style: disc; padding-left: var(--space-6); }
.legal-page a { color: var(--color-primary); }

/* SEO Content Block */
.seo-content-block {
  background: var(--color-surface);
  border-radius: var(--radius-md);
  padding: var(--space-5);
  border: 1px solid var(--color-border);
}
.seo-content-block h2 {
  font-size: var(--text-lg);
  font-weight: 600;
  margin-bottom: var(--space-3);
}
.seo-content-block p {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.7;
  margin-bottom: var(--space-2);
}
.seo-content-block p:last-child { margin-bottom: 0; }

/* =============================================
   RIGHT SIDEBAR
   ============================================= */
.sidebar-right {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  position: sticky;
  top: calc(var(--header-h) + var(--space-4));
}

.trending-block {
  background: var(--color-surface);
  border-radius: var(--radius-md);
  padding: var(--space-4);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-sm);
}
.trending-badge {
  display: inline-block;
  background: #FEF3C7;
  color: #92400E;
  font-size: var(--text-xs);
  font-weight: 700;
  padding: 2px 8px;
  border-radius: var(--radius-full);
  margin-left: var(--space-2);
  vertical-align: middle;
}
.trending-list { display: flex; flex-direction: column; gap: var(--space-3); }
.trending-item { display: flex; flex-direction: column; gap: var(--space-1); }
.trending-item a {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text);
  line-height: 1.4;
}
.trending-item a:hover { color: var(--color-primary); }
.trending-tag {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  background: var(--color-bg);
  padding: 2px 8px;
  border-radius: var(--radius-full);
  align-self: flex-start;
}

.tip-block {
  background: linear-gradient(135deg, #EFF6FF 0%, #DBEAFE 100%);
  border-radius: var(--radius-md);
  padding: var(--space-4);
  border: 1px solid #BFDBFE;
}
.tip-block h3 { font-size: var(--text-sm); font-weight: 700; margin-bottom: var(--space-2); }
.tip-block p { font-size: var(--text-sm); color: var(--color-text-muted); line-height: 1.6; margin-bottom: var(--space-3); }
.tip-cta {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-primary);
}
.tip-cta:hover { text-decoration: underline; }

/* =============================================
   POPULAR CALCULATORS GRID
   ============================================= */
.popular-section {
  padding: var(--space-10) var(--space-4);
}
.section-title {
  font-size: var(--text-2xl);
  font-weight: 700;
  margin-bottom: var(--space-6);
}
.popular-grid {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: var(--space-4);
}
.popular-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-5) var(--space-4);
  background: var(--color-surface);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  text-align: center;
  transition: box-shadow .2s, transform .2s, border-color .2s;
  text-decoration: none;
}
.popular-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
  border-color: var(--color-primary);
  text-decoration: none;
}
.popular-icon { font-size: 2rem; }
.popular-name { font-size: var(--text-sm); font-weight: 700; color: var(--color-text); }
.popular-desc { font-size: var(--text-xs); color: var(--color-text-muted); }

/* =============================================
   FOOTER
   ============================================= */
.site-footer {
  background: var(--key-num-bg);
  color: #94A3B8;
  padding-top: var(--space-10);
}
.footer-inner {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: var(--space-8);
  padding-bottom: var(--space-8);
}
.footer-brand .logo-text {
  font-size: var(--text-xl);
  font-weight: 700;
  color: #FFFFFF;
  display: block;
  margin-bottom: var(--space-2);
}
.footer-brand p { font-size: var(--text-sm); line-height: 1.6; }
.footer-nav h4 {
  font-size: var(--text-sm);
  font-weight: 700;
  color: #FFFFFF;
  margin-bottom: var(--space-3);
  text-transform: uppercase;
  letter-spacing: .06em;
}
.footer-nav ul { display: flex; flex-direction: column; gap: var(--space-2); }
.footer-nav a { font-size: var(--text-sm); color: #94A3B8; }
.footer-nav a:hover { color: #FFFFFF; text-decoration: none; }
.footer-seo h4 {
  font-size: var(--text-sm);
  font-weight: 700;
  color: #FFFFFF;
  margin-bottom: var(--space-3);
  text-transform: uppercase;
  letter-spacing: .06em;
}
.footer-keywords { display: flex; flex-direction: column; gap: var(--space-2); }
.footer-keywords a { font-size: var(--text-xs); color: #64748B; }
.footer-keywords a:hover { color: #94A3B8; text-decoration: none; }

/* =============================================
   LEGAL PAGES (disclaimer / terms / privacy)
   ============================================= */
.legal-page {
  max-width: 800px;
  margin: var(--space-10) auto;
  padding: 0 var(--space-4) var(--space-12);
}
.legal-page h1 {
  font-size: var(--text-3xl);
  font-weight: 700;
  margin-bottom: var(--space-2);
  color: var(--color-text);
}
.legal-meta {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-8);
  padding-bottom: var(--space-4);
  border-bottom: 1px solid var(--color-border);
}
.legal-page h2 {
  font-size: var(--text-lg);
  font-weight: 600;
  margin: var(--space-8) 0 var(--space-3);
  color: var(--color-text);
}
.legal-page p {
  font-size: var(--text-base);
  color: var(--color-text-muted);
  line-height: 1.8;
  margin-bottom: var(--space-3);
}
.legal-page ul {
  list-style: disc;
  padding-left: var(--space-6);
  margin-bottom: var(--space-4);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}
.legal-page li {
  font-size: var(--text-base);
  color: var(--color-text-muted);
  line-height: 1.7;
}
.legal-page a { color: var(--color-primary); }
.legal-page a:hover { text-decoration: underline; }

/* Inline calculator disclaimer */
.calc-disclaimer {
  margin-top: var(--space-4);
  padding: var(--space-3) var(--space-4);
  background: #FFFBEB;
  border: 1px solid #FDE68A;
  border-radius: var(--radius-sm);
  font-size: var(--text-xs);
  color: #92400E;
  line-height: 1.6;
}
.calc-disclaimer a {
  color: #92400E;
  font-weight: 600;
  text-decoration: underline;
}

/* Footer disclaimer block */
.footer-disclaimer {
  background: #0F172A;
  border-top: 1px solid #1E293B;
  padding: var(--space-5) 0;
}
.footer-disclaimer p {
  font-size: var(--text-xs);
  color: #475569;
  line-height: 1.7;
  max-width: 900px;
}
.footer-disclaimer strong { color: #64748B; }

.footer-bottom {
  border-top: 1px solid #334155;
  padding: var(--space-4) 0;
  text-align: center;
  font-size: var(--text-xs);
  color: #475569;
}
.footer-bottom a { color: #64748B; }
.footer-bottom a:hover { color: #94A3B8; }

/* ---- Legal Pages (disclaimer / terms / privacy) ---- */
.legal-page {
  max-width: 800px;
  margin: var(--space-10) auto;
  padding: 0 var(--space-4) var(--space-12);
}
.legal-page h1 {
  font-size: var(--text-3xl);
  font-weight: 700;
  margin-bottom: var(--space-2);
  color: var(--color-text);
}
.legal-meta {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-8);
  padding-bottom: var(--space-4);
  border-bottom: 1px solid var(--color-border);
}
.legal-page h2 {
  font-size: var(--text-xl);
  font-weight: 600;
  margin: var(--space-8) 0 var(--space-3);
  color: var(--color-text);
}
.legal-page p {
  font-size: var(--text-base);
  color: var(--color-text-muted);
  line-height: 1.8;
  margin-bottom: var(--space-3);
}
.legal-page ul {
  list-style: disc;
  padding-left: var(--space-6);
  margin-bottom: var(--space-4);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}
.legal-page li {
  font-size: var(--text-base);
  color: var(--color-text-muted);
  line-height: 1.7;
}
.legal-page a { color: var(--color-primary); }
.legal-page a:hover { text-decoration: underline; }

/* =============================================
   FORM CALCULATORS
   ============================================= */

/* Container transition */
#calc-container {
  transition: opacity 0.15s ease;
}

/* Form card header */
.calc-form-card { padding: var(--space-6); }
.calc-form-header {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  margin-bottom: var(--space-5);
}
.calc-form-icon { font-size: 1.75rem; line-height: 1; }
.calc-form-card .calc-title {
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-text);
  margin: 0;
}

/* Form layout */
.calc-form {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}
.form-field {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}
.field-label {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text);
}
.field-hint {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  margin: 0;
}

/* Inputs */
.calc-input {
  width: 100%;
  padding: var(--space-3) var(--space-3);
  background: var(--color-bg);
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-sm);
  font-size: var(--text-base);
  color: var(--color-text);
  font-family: var(--font-base);
  transition: border-color 0.15s, box-shadow 0.15s;
  box-sizing: border-box;
}
.calc-input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37,99,235,0.15);
}
.calc-input::placeholder { color: #94A3B8; }

/* Radio group */
.radio-group {
  display: flex;
  gap: var(--space-4);
  flex-wrap: wrap;
}
.radio-label {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  color: var(--color-text);
  cursor: pointer;
}
.radio-label input[type=radio] { accent-color: var(--color-primary); }

/* Range slider */
.range-wrapper {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}
.calc-range {
  flex: 1;
  accent-color: var(--color-primary);
  height: 4px;
  cursor: pointer;
}
.range-output {
  min-width: 3rem;
  text-align: right;
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--color-primary);
}

/* Calculate button */
.btn-calculate {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  background: var(--key-eq-bg);
  color: #fff;
  border: none;
  border-radius: var(--radius-sm);
  font-size: var(--text-base);
  font-weight: 700;
  cursor: pointer;
  transition: filter 0.15s, transform 0.1s;
  margin-top: var(--space-2);
}
.btn-calculate:hover  { filter: brightness(1.1); }
.btn-calculate:active { transform: scale(0.98); }

/* Result block */
.calc-form-result {
  margin-top: var(--space-4);
  padding: var(--space-4);
  background: #F0FDF4;
  border: 1.5px solid #86EFAC;
  border-radius: var(--radius-sm);
  animation: fadeInUp 0.2s ease;
}
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(6px); }
  to   { opacity: 1; transform: translateY(0); }
}
.result-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-3);
}
.result-grid-single { grid-template-columns: 1fr; }
.result-item {
  display: flex;
  flex-direction: column;
  gap: 2px;
}
.result-label {
  font-size: var(--text-xs);
  color: #166534;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}
.result-value {
  font-size: var(--text-xl);
  font-weight: 700;
  color: #15803D;
  font-variant-numeric: tabular-nums;
}
.result-large { font-size: var(--text-2xl); }
.result-note {
  margin: var(--space-3) 0 0;
  font-size: var(--text-xs);
  color: #166534;
  opacity: 0.8;
}
.result-error {
  color: #DC2626;
  font-size: var(--text-sm);
  font-weight: 600;
  margin: 0;
}

/* BMI category colors */
.bmi-under  { color: #3B82F6 !important; }
.bmi-normal { color: #10B981 !important; }
.bmi-over   { color: #F59E0B !important; }
.bmi-obese  { color: #EF4444 !important; }

/* BMI visual scale */
.bmi-scale { margin-top: var(--space-4); }
.bmi-scale-bar {
  position: relative;
  display: flex;
  height: 12px;
  border-radius: var(--radius-full);
  overflow: visible;
  margin-bottom: var(--space-1);
}
.bmi-scale-seg { display: block; height: 100%; }
.bmi-scale-seg:first-child { border-radius: var(--radius-full) 0 0 var(--radius-full); }
.bmi-scale-seg:last-child  { border-radius: 0 var(--radius-full) var(--radius-full) 0; }
.bmi-under-bg  { background: #93C5FD; }
.bmi-normal-bg { background: #6EE7B7; }
.bmi-over-bg   { background: #FCD34D; }
.bmi-obese-bg  { background: #FCA5A5; }
.bmi-scale-marker {
  position: absolute;
  top: 50%;
  transform: translate(-50%, -50%);
  width: 16px;
  height: 16px;
  background: #fff;
  border: 3px solid #1E293B;
  border-radius: 50%;
  box-shadow: 0 1px 4px rgba(0,0,0,.2);
  z-index: 2;
}
.bmi-scale-labels {
  display: flex;
  justify-content: space-between;
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  margin-bottom: 2px;
}
.bmi-scale-cats {
  display: flex;
  font-size: 10px;
  color: var(--color-text-muted);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: .03em;
}
.bmi-scale-cats span { text-align: center; }

/* =============================================
   RESPONSIVE – Tablet (≤1024px)
   ============================================= */
@media (max-width: 1024px) {
  .main-layout {
    grid-template-columns: 1fr 280px;
    grid-template-areas:
      "calc sidebar-right"
      "calc sidebar-right";
  }
  .sidebar-left { display: none; }
  .popular-grid { grid-template-columns: repeat(3, 1fr); }
  .footer-inner { grid-template-columns: 1fr 1fr; gap: var(--space-6); }
  .ad-top .ad-placeholder,
  .ad-bottom .ad-placeholder { width: 100%; max-width: 728px; }
}

/* =============================================
   RESPONSIVE – Mobile (≤768px)
   ============================================= */
@media (max-width: 768px) {
  :root { --header-h: 56px; }

  .main-nav { display: none; }
  .nav-toggle { display: flex; }

  /* Mobile nav open state */
  .main-nav.nav-open {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: var(--header-h);
    left: 0;
    right: 0;
    background: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    padding: var(--space-4);
    z-index: 100;
    box-shadow: 0 4px 12px rgba(0,0,0,.12);
  }
  .main-nav.nav-open ul {
    flex-direction: column;
    gap: 0;
  }
  .main-nav.nav-open > ul > li { border-bottom: 1px solid var(--color-border); }
  .main-nav.nav-open > ul > li:last-child { border-bottom: none; }
  .main-nav.nav-open a { padding: var(--space-3) 0; display: block; }
  .main-nav.nav-open .dropdown {
    position: static;
    opacity: 1;
    visibility: visible;
    transform: none;
    box-shadow: none;
    border: none;
    padding: 0 0 var(--space-2) var(--space-4);
    background: transparent;
  }
  .main-nav.nav-open .has-dropdown.open .dropdown { display: block; }
  .main-nav.nav-open .dropdown a { padding: var(--space-2) 0; font-size: var(--text-sm); }

  .main-layout {
    grid-template-columns: 1fr;
    grid-template-areas: "calc" "sidebar-right";
    padding-top: var(--space-4);
    gap: var(--space-4);
  }
  .sidebar-right { position: static; }
  .ad-300x600 { display: none; }

  .calc-card { max-width: 100%; padding: var(--space-4); }
  .btn { height: 60px; font-size: var(--text-lg); }

  .popular-grid { grid-template-columns: repeat(2, 1fr); }
  .section-title { font-size: var(--text-xl); }

  .footer-inner { grid-template-columns: 1fr; gap: var(--space-5); }

  .ad-top .ad-placeholder,
  .ad-bottom .ad-placeholder { width: 320px; height: 50px; }
}

/* =============================================
   RESPONSIVE – Small Mobile (≤375px)
   ============================================= */
@media (max-width: 375px) {
  .btn { height: 52px; font-size: var(--text-base); border-radius: var(--radius-sm); }
  .calc-result { font-size: var(--text-3xl); }
  .popular-grid { grid-template-columns: repeat(2, 1fr); gap: var(--space-3); }
}

/* Share button */
.btn-share {
  margin-left: auto;
  background: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: var(--space-1) var(--space-3);
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--color-text-muted);
  cursor: pointer;
  transition: border-color .15s, color .15s;
  white-space: nowrap;
}
.btn-share:hover { border-color: var(--color-primary); color: var(--color-primary); }

/* Inline field validation */
.calc-input.input-error {
  border-color: #EF4444;
  box-shadow: 0 0 0 3px rgba(239,68,68,0.15);
}
.field-error {
  font-size: var(--text-xs);
  color: #DC2626;
  margin: var(--space-1) 0 0;
}

/* Copy result button */
.btn-copy-result {
  display: block;
  margin-top: var(--space-3);
  margin-left: auto;
  background: none;
  border: 1px solid #86EFAC;
  border-radius: var(--radius-sm);
  padding: var(--space-1) var(--space-3);
  font-size: var(--text-xs);
  font-weight: 600;
  color: #166534;
  cursor: pointer;
  transition: background .15s, color .15s;
}
.btn-copy-result:hover { background: #DCFCE7; }

/* Tip quick reference */
.tip-quick-ref {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  flex-wrap: wrap;
  margin-top: var(--space-3);
  padding-top: var(--space-3);
  border-top: 1px solid #86EFAC;
  font-size: var(--text-xs);
}
.tip-quick-label {
  color: #166534;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: .04em;
}
.tip-quick-item {
  color: #15803D;
  background: #DCFCE7;
  padding: 2px 8px;
  border-radius: var(--radius-full);
}
.tip-quick-item strong { margin-right: 4px; }

/* Amortization details toggle */
.amort-summary {
  margin-top: var(--space-3);
  border-top: 1px solid #86EFAC;
  padding-top: var(--space-3);
}
.amort-summary summary {
  font-size: var(--text-sm);
  font-weight: 600;
  color: #166534;
  cursor: pointer;
  user-select: none;
  list-style: none;
  display: flex;
  align-items: center;
  gap: var(--space-2);
}
.amort-summary summary::before {
  content: '▶';
  font-size: 0.6rem;
  transition: transform .2s;
}
.amort-summary[open] summary::before { transform: rotate(90deg); }
.amort-summary summary::-webkit-details-marker { display: none; }

/* Back to Top */
.back-to-top {
  position: fixed;
  bottom: var(--space-6);
  right: var(--space-6);
  width: 44px;
  height: 44px;
  border-radius: var(--radius-full);
  background: var(--color-primary);
  color: #fff;
  border: none;
  font-size: var(--text-lg);
  cursor: pointer;
  box-shadow: var(--shadow-md);
  transition: opacity .2s, transform .2s;
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: center;
}
.back-to-top:hover { background: var(--color-primary-dk); transform: translateY(-2px); }
.back-to-top[hidden] { display: none; }

/* =============================================
   PRINT
   ============================================= */
@media print {
  .site-header, .sidebar-left, .sidebar-right,
  .ad-banner, .ad-sidebar, .popular-section,
  .site-footer, .nav-toggle, .breadcrumb,
  .btn-calculate, .calc-disclaimer { display: none !important; }

  body { background: #fff; color: #000; font-size: 12pt; }
  .main-layout { display: block; }
  .calc-main { max-width: 100%; }
  .calc-card { box-shadow: none; border: 1px solid #ccc; max-width: 100%; }
  .calc-form-result { border: 1px solid #ccc; background: #f9f9f9; }
  .result-value { color: #000; }
  .legal-page { margin: 0; padding: 0; max-width: 100%; }
  a[href]::after { content: " (" attr(href) ")"; font-size: 10pt; color: #555; }
  a[href^="#"]::after { content: ""; }
}