/* css/style.css */
:root {
  --blue: #1a73e8;
  --blue-dark: #1557b0;
  --blue-light: #e8f0fe;
  --green: #137333;
  --green-light: #e6f4ea;
  --red: #c5221f;
  --red-light: #fce8e6;
  --amber: #7d5700;
  --amber-light: #fef7e0;
  --text: #202124;
  --text-secondary: #5f6368;
  --border: #dadce0;
  --surface: #f8f9fa;
  --white: #ffffff;
  --radius: 8px;
  --radius-lg: 12px;
  --radius-pill: 100px;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.12);
  --font-body: 'Roboto', sans-serif;
  --font-heading: 'Nunito', sans-serif;
  --transition: 0.15s ease;
}

/* Reset and Base Styles */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-body);
  color: var(--text);
  background-color: var(--surface);
  line-height: 1.7;
  font-size: 16px;
  font-weight: 400;
  overflow-x: hidden;
  width: 100%;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

/* Typography Scale (Mobile First) */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  color: var(--text);
}

h1 {
  font-size: 22px;
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: 1rem;
}

h2 {
  font-size: 18px;
  font-weight: 600;
  line-height: 1.4;
  margin-bottom: 1rem;
}

h3 {
  font-size: 18px;
  font-weight: 600;
  line-height: 1.4;
  margin-bottom: 0.75rem;
}

label {
  display: block;
  font-size: 13px;
  font-weight: 500;
  margin-bottom: 6px;
  color: var(--text);
}

.micro {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--text-secondary);
}

p.subtitle {
  font-size: 16px;
  color: var(--text-secondary);
  margin-bottom: 30px;
}

@media (min-width: 900px) {
  h1 { font-size: 28px; }
  h2 { font-size: 22px; }
}

/* Base Layout Constraints */
/* Base Layout Constraints */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

@media (min-width: 600px) {
  .container { padding: 0 24px; }
}

main {
  width: 100%;
  max-width: 800px; /* Default for text-heavy content */
  margin: 0 auto;
}

/* On index.html, we use a wider main container */
.site-main.home main {
  max-width: 1200px;
}

aside.sidebar {
  width: 100%;
  max-width: 800px;
  margin: 40px auto 0;
}

@media (min-width: 900px) {
  .page-layout-grid {
    display: grid;
    grid-template-columns: 1fr 300px;
    gap: 40px;
    max-width: 1200px;
    margin: 40px auto;
    align-items: start;
    padding: 0 24px;
  }
  
  main {
    max-width: none;
    margin: 0;
  }
  
  aside.sidebar {
    max-width: none;
    margin: 0;
    position: sticky;
    top: 84px;
  }
}

/* Standard Components */
.calculator-card {
  background-color: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 40px;
}
@media (min-width: 600px) {
  .calculator-card { padding: 24px; }
}

.calculator-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 24px;
}

.explanation, .formula, .related, .faq {
  margin-bottom: 40px;
  background-color: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px;
  box-shadow: var(--shadow-sm);
}

@media (min-width: 600px) {
  .explanation, .formula, .related, .faq {
    padding: 24px;
  }
}

.explanation p, .formula p {
  color: var(--text-secondary);
  margin-bottom: 12px;
}
.explanation p:last-child, .formula p:last-child {
  margin-bottom: 0;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  font-family: var(--font-body);
  transition: all var(--transition);
  cursor: pointer;
  border: 1px solid transparent;
}

.btn-primary {
  background-color: var(--blue);
  color: var(--white);
  border: none;
  border-radius: var(--radius-pill);
  padding: 10px 28px;
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: background-color var(--transition);
  font-family: var(--font-body);
}
.btn-primary:hover {
  background-color: var(--blue-dark);
}

.btn-secondary {
  background-color: var(--white);
  color: var(--blue);
  border: 1px solid var(--border);
  border-radius: var(--radius-pill);
  padding: 10px 28px;
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: background-color var(--transition);
  font-family: var(--font-body);
}
.btn-secondary:hover {
  background-color: var(--surface);
}

/* Inputs */
.input-group {
  margin-bottom: 20px;
  display: flex;
  flex-direction: column;
}

input[type="text"],
input[type="number"],
input[type="date"],
select {
  width: 100%;
  height: 40px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0 12px;
  font-size: 15px;
  font-family: var(--font-body);
  color: var(--text);
  background-color: var(--white);
  transition: all var(--transition);
}

input:focus,
select:focus {
  outline: none;
  border-color: var(--blue);
  box-shadow: 0 0 0 3px rgba(26,115,232,0.12);
}

input::placeholder {
  color: var(--text-secondary);
}

.input-error {
  border-color: var(--red) !important;
}

.error-message {
  color: var(--red);
  font-size: 13px;
  margin-top: 4px;
}

/* Result Box */
.result-box {
  background-color: var(--blue-light);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin-top: 24px;
  text-align: center;
  transition: opacity 0.3s ease;
  opacity: 1;
}

.result-box.hidden {
  display: none;
  opacity: 0;
}

.result-value {
  font-size: 32px;
  font-family: var(--font-heading);
  color: var(--blue-dark);
  font-weight: 700;
  margin: 10px 0;
}

.result-label {
  font-size: 16px;
  color: var(--text);
  font-weight: 500;
}

.result-sub {
  font-size: 14px;
  color: var(--text-secondary);
}

/* FAQ Accordion */
.faq-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.faq-item {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background-color: var(--white);
  overflow: hidden;
}

.faq-question {
  padding: 16px 20px;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  user-select: none;
  font-family: var(--font-heading);
  font-weight: 600;
  font-size: 16px;
  color: var(--text);
  margin: 0;
  transition: background-color var(--transition);
}

.faq-question:hover {
  background-color: var(--surface);
}

.faq-icon {
  width: 20px;
  height: 20px;
  transition: transform 0.3s ease;
  fill: var(--text-secondary);
}

.faq-item.active .faq-icon {
  transform: rotate(180deg);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease-out, padding 0.3s ease;
  color: var(--text-secondary);
}

.faq-item.active .faq-answer {
  padding: 0 20px 16px 20px;
}

.faq-answer p {
  margin-bottom: 12px;
}
.faq-answer p:last-child {
  margin-bottom: 0;
}

/* Grid Layouts for Formula, Related, Categories, Sidebar */
.category-overview {
  margin: 40px 0;
}
.category-overview h2 {
  text-align: center;
  margin-bottom: 30px;
}
.category-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
}
@media (min-width: 480px) {
  .category-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (min-width: 768px) {
  .category-grid { 
    grid-template-columns: repeat(3, 1fr); 
    gap: 20px;
  }
}
@media (min-width: 1024px) {
  .category-grid { grid-template-columns: repeat(4, 1fr); }
}
.category-card {
  background-color: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px 12px;
  text-align: center;
  text-decoration: none;
  transition: all var(--transition);
  display: flex;
  flex-direction: column;
  align-items: center;
  box-shadow: var(--shadow-sm);
}
.category-card:hover {
  transform: translateY(-4px);
  border-color: var(--blue);
  box-shadow: 0 4px 12px rgba(26,115,232,0.15);
}
.category-icon {
  width: 48px;
  height: 48px;
  background-color: var(--blue-light);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 12px;
}
.category-icon svg {
  width: 24px;
  height: 24px;
  fill: var(--blue);
}
.category-name {
  color: var(--text);
  font-weight: 600;
  font-size: 14px;
  margin-bottom: 4px;
  line-height: 1.2;
}
@media (min-width: 600px) {
  .category-name { font-size: 16px; }
}
.category-count {
  color: var(--text-secondary);
  font-size: 12px;
}

.formula-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 20px;
  margin-top: 16px;
}
@media (min-width: 900px) {
  .formula-grid { grid-template-columns: repeat(3, 1fr); }
}

.formula-card-item {
  background-color: var(--surface);
  padding: 16px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
}

.related-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(100%, 1fr));
  gap: 16px;
  margin-top: 16px;
}
@media (min-width: 600px) {
  .related-grid { grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); }
}

.related-card {
  display: block;
  text-decoration: none;
  background-color: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  transition: all var(--transition);
}
.related-card:hover {
  border-color: var(--blue);
  box-shadow: var(--shadow-sm);
  transform: translateY(-2px);
}
.related-card h3 {
  color: var(--blue);
  font-size: 16px;
  margin-bottom: 8px;
}
.related-card p {
  color: var(--text-secondary);
  font-size: 13px;
  margin: 0;
}

/* Sidebar Specific */
.ad-sidebar {
  min-height: 250px;
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  margin-bottom: 24px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
  font-size: 13px;
} /* This will wrap the AdSense injection */

.sidebar-nav {
  background-color: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px;
  box-shadow: var(--shadow-sm);
}

.sidebar-nav h3 {
  font-size: 16px;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border);
}

.sidebar-nav ul {
  list-style: none;
}

.sidebar-nav li {
  margin-bottom: 12px;
}
.sidebar-nav li:last-child {
  margin-bottom: 0;
}

.sidebar-nav a {
  text-decoration: none;
  color: var(--text);
  font-size: 14px;
  transition: color var(--transition);
}
.sidebar-nav a:hover {
  color: var(--blue);
  text-decoration: underline;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--white);
  border-bottom: 1px solid var(--border);
}

.header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 140px;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}
@media (min-width: 600px) {
  .header-container { padding: 0 24px; }
}

.site-logo {
  display: flex;
  align-items: center;
  height: 100%;
}

.site-logo img {
  height: 120px;
  width: auto;
  display: block;
}

@media (max-width: 600px) {
  .header-container { height: 120px; }
  .site-logo img { height: 130px; }
}

.main-nav {
  display: none;
}
@media (min-width: 1100px) {
  .main-nav {
    display: flex;
    gap: 16px;
    align-items: center;
  }
}

.main-nav a {
  text-decoration: none;
  color: var(--text);
  font-size: 13px;
  font-weight: 500;
  transition: color var(--transition);
  white-space: nowrap;
}
.main-nav a:hover,
.main-nav a.active {
  color: var(--blue);
}

.mobile-menu-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
}
@media (min-width: 1100px) {
  .mobile-menu-btn { display: none; }
}

.hamburger-line {
  display: block;
  width: 24px;
  height: 2px;
  background-color: var(--text);
  position: relative;
  transition: background-color var(--transition);
}
.hamburger-line::before,
.hamburger-line::after {
  content: '';
  position: absolute;
  width: 24px;
  height: 2px;
  background-color: var(--text);
  left: 0;
  transition: transform var(--transition);
}
.hamburger-line::before { top: -6px; }
.hamburger-line::after { bottom: -6px; }

/* Mobile Dropdown */
.mobile-nav-dropdown {
  position: absolute;
  top: 140px;
  left: 0;
  right: 0;
  background-color: var(--white);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow-sm);
  padding: 10px 0;
  display: none;
  flex-direction: column;
}

@media (max-width: 600px) {
  .mobile-nav-dropdown { top: 120px; }
}
.mobile-nav-dropdown.active {
  display: flex;
}
.mobile-nav-dropdown a {
  padding: 12px 20px;
  text-decoration: none;
  color: var(--text);
  font-size: 16px;
  border-bottom: 1px solid var(--surface);
}
.mobile-nav-dropdown a:last-child {
  border-bottom: none;
}

/* Footer */
.site-footer {
  background-color: var(--surface);
  border-top: 1px solid var(--border);
  padding: 40px 0 20px;
  margin-top: 60px;
}

.footer-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}
@media (min-width: 600px) {
  .footer-container { padding: 0 24px; }
}

.footer-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 20px;
  margin-bottom: 24px;
}
.footer-nav a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 14px;
  transition: color var(--transition);
}
.footer-nav a:hover {
  color: var(--blue);
  text-decoration: underline;
}

.footer-bottom {
  display: flex;
  flex-direction: column;
  gap: 12px;
  border-top: 1px solid var(--border);
  padding-top: 20px;
}
@media (min-width: 600px) {
  .footer-bottom {
    flex-direction: row;
    justify-content: space-between;
    align-items: center;
  }
}

.footer-copyright {
  color: var(--text-secondary);
  font-size: 13px;
}

.footer-tagline {
  color: var(--text-secondary);
  font-size: 13px;
}

/* Helper Grid for Inputs */
.grid-2 {
  display: grid;
  grid-template-columns: 1fr;
  gap: 20px;
}
@media (min-width: 600px) {
  .grid-2 { grid-template-columns: repeat(2, 1fr); }
}

.grid-auto {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 20px;
}

/* Breadcrumb Navigation */
.breadcrumb {
  margin-bottom: 24px;
  font-size: 13px;
  color: var(--text-secondary);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px;
}
.breadcrumb a {
  color: var(--blue);
  text-decoration: none;
  transition: color var(--transition);
}
.breadcrumb a:hover {
  text-decoration: underline;
  color: var(--blue-dark);
}
.breadcrumb-separator {
  color: var(--text-secondary);
}

/* Scientific Calculator - iOS / Phone Style */
.scientific-calc-wrapper {
  background-color: #000000;
  border-radius: 40px;
  padding: 24px;
  box-shadow: 0 20px 40px rgba(0,0,0,0.4);
  max-width: 320px;
  margin: 0 auto 40px;
  border: 4px solid #333;
}

.scientific-display {
  background-color: transparent;
  padding: 40px 10px 10px;
  text-align: right;
  margin-bottom: 10px;
}

.scientific-display-main {
  color: #ffffff;
  font-size: 64px;
  font-family: var(--font-body);
  font-weight: 300;
  line-height: 1;
  word-break: break-all;
}

.scientific-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
}

.scientific-btn {
  width: 60px;
  height: 60px;
  border-radius: 50%;
  border: none;
  font-family: var(--font-body);
  font-size: 22px;
  font-weight: 400;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: filter 0.1s ease;
  background-color: #333333;
  color: #ffffff;
}

.scientific-btn:active {
  filter: brightness(1.5);
}

.scientific-btn.special {
  background-color: #a5a5a5;
  color: #000000;
}

.scientific-btn.operator {
  background-color: #fe9505;
  color: #ffffff;
  font-size: 28px;
}

.scientific-btn.zero {
  grid-column: span 2;
  width: 100%;
  border-radius: 30px;
  justify-content: flex-start;
  padding-left: 24px;
}

@media (max-width: 400px) {
  .scientific-calc-wrapper {
    max-width: 100%;
    padding: 12px;
    border-radius: 30px;
  }
  .scientific-display-main {
    font-size: 48px;
  }
  .scientific-grid {
    gap: 8px;
  }
  .scientific-btn {
    width: 100%;
    aspect-ratio: 1 / 1;
    height: auto;
    font-size: 18px;
  }
  .scientific-btn.zero {
    aspect-ratio: auto;
    height: auto;
    padding: 12px 20px;
  }
}

/* Hero Section */
.hero {
  text-align: center;
  padding: 40px 0;
  max-width: 800px;
  margin: 0 auto;
}

.hero h1 {
  margin-bottom: 16px;
}

.hero .subtitle {
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.scientific-history-panel {
  margin-top: 24px;
  border-top: 1px solid #3c4043;
  padding-top: 16px;
  color: #9aa0a6;
  font-size: 13px;
  max-height: 150px;
  overflow-y: auto;
}
.scientific-history-item { margin-bottom: 8px; }