/* ==========================================
   Global Styles
   ========================================== */

/* ==========================================
   CSS Import Hierarchy - Order Critical!
   ========================================== */

/* 1. Foundation Layer */
@import url('variables.css');    /* Design tokens & custom properties */
@import url('reset.css');        /* Browser normalization */

/* 2. Component Layer */
@import url('calculator.css');   /* Calculator component */
@import url('guide.css');        /* Guide sections */

/* 3. UI Layer */
@import url('modal.css');        /* Modal dialogs */
@import url('toast.css');        /* Toast notifications */

/* ==========================================
   Global Typography System
   ========================================== */

/* Base Typography */
body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  font-family: var(--font-primary);
  font-size: var(--text-base);
  line-height: var(--leading-normal);
  color: var(--text-primary-90);
}

/* Heading Hierarchy */
h1, h2, h3, h4, h5, h6 {
  margin: var(--spacing-8) 0 var(--spacing-3);
  line-height: var(--leading-tight);
  font-weight: var(--font-bold);
  color: var(--text-primary);
}

h1 {
  margin-top: 0;
  font-size: var(--text-2xl);
}

h2 {
  margin-top: var(--spacing-10);
  padding-bottom: var(--spacing-2);
  border-bottom: var(--border-width-2) solid var(--primary);
  font-size: var(--text-xl);
  font-weight: var(--font-semibold);
}

h3 {
  font-size: var(--text-lg);
  color: var(--primary);
}

h4 {
  font-size: var(--text-base);
  font-weight: var(--font-semibold);
}

h5, h6 {
  font-size: var(--text-sm);
  font-weight: var(--font-semibold);
}

h6 {
  letter-spacing: var(--tracking-wide);
  text-transform: uppercase;
}

/* Text Elements */
p {
  line-height: var(--leading-relaxed);
}

strong {
  font-weight: var(--font-semibold);
  color: var(--text-primary);
}

em {
  font-style: italic;
  color: var(--primary);
}

small {
  font-size: var(--text-sm);
  color: var(--text-muted);
}

/* Links */
a {
  text-decoration: underline;
  text-underline-offset: 2px;
  color: var(--primary);
  transition: color var(--transition-fast);
}

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

/* Lists */
ul, ol {
  margin: var(--spacing-4) 0;
  padding-left: var(--spacing-6);
  list-style: none;
}

li {
  position: relative;
  margin-bottom: var(--spacing-3);
  line-height: var(--leading-relaxed);
}

ul li::before,
ol li::before {
  position: absolute;
  left: calc(-1 * var(--spacing-6));
  font-weight: var(--font-semibold);
  color: var(--primary);
}

ul li::before {
  content: '•';
  font-size: var(--text-base);
}

ol {
  counter-reset: list-counter;
}

ol li {
  counter-increment: list-counter;
}

ol li::before {
  content: counter(list-counter) '.';
  font-family: var(--font-accent);
}

/* Nested Lists */
ul ul, ol ol, ul ol, ol ul {
  margin: var(--spacing-2) 0;
  padding-left: var(--spacing-4);
}

/* ==========================================
   Math Formulas Typography
   ========================================== */

.math-formula-block {
  position: relative;
  margin: var(--spacing-3) 0;
  padding: var(--spacing-2);
  border-radius: var(--radius-lg);
  background: var(--background);
  box-shadow: var(--shadow-inset);
}

.formula-notation {
  margin: var(--spacing-1) 0;
  font-family: var(--font-monospace);
  font-size: var(--text-sm);
  line-height: var(--leading-relaxed);
  text-align: center;
  color: var(--text-primary-90);
}

/* Fraction Display - Inline on Mobile */
.math-fraction {
  display: inline;
  margin: 0;
}

.math-numerator,
.math-denominator {
  display: inline;
  font-family: var(--font-monospace);
  font-size: var(--text-sm);
  color: var(--text-primary-90);
}

.math-numerator::after {
  content: " / ";
  color: var(--text-primary-90);
}

/* Math Operators */
.math-operator {
  display: inline;
  margin: 0 var(--spacing-px);
  font-family: var(--font-monospace);
  font-size: var(--text-sm);
  color: var(--text-primary-90);
}

/* Step Numbers - Hidden on Mobile */
.formula-step-number {
  display: none;
}

/* Responsive Typography Scale */
@media (min-width: 768px) {
  h1 { font-size: var(--text-4xl); }
  h2 { font-size: var(--text-3xl); }
  h3 { font-size: var(--text-2xl); }
  h4 { font-size: var(--text-xl); }
  h5 { font-size: var(--text-lg); }
  h6 { font-size: var(--text-base); }
  
  /* Math Formulas - Tablet */
  .math-formula-block {
    margin: var(--spacing-4) 0;
    padding: var(--spacing-4);
    border-radius: var(--radius-xl);
  }
  
  .formula-notation {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-2);
    margin: var(--spacing-2) 0;
    font-size: var(--text-base);
    flex-wrap: wrap;
  }
  
  .math-fraction {
    position: relative;
    display: inline-flex;
    flex-direction: column;
    align-items: center;
    margin: 0 var(--spacing-2);
    vertical-align: middle;
  }
  
  .math-numerator,
  .math-denominator {
    display: block;
    min-width: 5rem;
    padding: var(--spacing-1) var(--spacing-2);
    font-size: var(--text-base);
    text-align: center;
    color: var(--text-primary);
  }
  
  .math-numerator {
    border-bottom: var(--border-width-2) solid var(--primary);
  }
  
  .math-numerator::after {
    content: none;
  }
  
  .math-operator {
    display: inline-block;
    margin: 0 var(--spacing-2);
    font-size: var(--text-2xl);
    color: var(--primary);
  }
  
  .formula-step-number {
    position: absolute;
    top: var(--spacing-3);
    left: var(--spacing-3);
    display: flex;
    align-items: center;
    justify-content: center;
    width: var(--spacing-8);
    height: var(--spacing-8);
    border-radius: 50%;
    font-family: var(--font-accent);
    font-weight: var(--font-bold);
    color: var(--text-inverse);
    background: var(--primary);
  }
}

@media (min-width: 1024px) {
  h1 { font-size: var(--text-5xl); }
  h2 { 
    margin-top: var(--spacing-16);
    font-size: var(--text-4xl); 
  }
  h3 { font-size: var(--text-3xl); }
  h4 { font-size: var(--text-2xl); }
  
  /* Math Formulas - Desktop */
  .math-formula-block {
    padding: var(--spacing-6);
  }
  
  .formula-notation {
    gap: var(--spacing-3);
    font-size: var(--text-xl);
  }
  
  .math-numerator,
  .math-denominator {
    min-width: 6rem;
  }
}

/* ==========================================
   Header Component
   ========================================== */

header {
  position: fixed;
  z-index: var(--z-header);
  width: 100%;
  background: var(--background);
  transition: transform var(--transition-base), background-color var(--transition-base);
}

header.header-scrolled {
  box-shadow: var(--shadow-sm);
}

header.header-hidden {
  transform: translateY(-100%);
}

.header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  padding: var(--spacing-3);
}

/* Logo */
.logo {
  display: flex;
  align-items: center;
  flex-shrink: 0;
  min-width: 0;
  padding: var(--spacing-4) 0;
}

.logo img {
  width: auto;
  max-width: 100%;
  height: 3.157rem;
  transition: transform var(--transition-base);
}

/* Navigation */
nav {
  display: flex;
  align-items: center;
  flex-shrink: 1;
  min-width: 0;
}

nav ul {
  display: flex;
  align-items: center;
  gap: var(--spacing-8);
  margin: 0;
  padding: 0;
  flex-wrap: nowrap;
  min-width: 0;
  list-style: none;
}

header nav li::before {
  display: none;
}

/* Navigation Links */
nav a.txt {
  position: relative;
  padding: var(--spacing-2) 0;
  text-decoration: none;
  color: var(--text-primary);
  transition: color var(--transition-base);
}

nav a.txt::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: var(--border-width-2);
  background: var(--primary);
  transition: width var(--transition-base);
}

nav a.btn {
  display: inline-block;
  padding: var(--spacing-4) var(--spacing-8);
  border: var(--border-width-2) solid var(--background);
  border-radius: var(--radius-lg);
  text-decoration: none;
  text-transform: uppercase;
  color: var(--background);
  background: var(--success);
  cursor: pointer;
  transition: all var(--transition-base);
}

/* Mobile Menu Button */
.mobile-menu-btn {
  position: relative;
  display: none;
  width: 1.875rem;
  height: 1.875rem;
  padding: var(--spacing-4);
  border: none;
  background: none;
  color: var(--text-primary);
  cursor: pointer;
  transition: all var(--transition-base);
}

.mobile-menu-btn span {
  position: absolute;
  left: 0;
  display: block;
  width: 100%;
  height: var(--border-width-2);
  background: var(--text-primary);
  transition: all var(--transition-base);
}

.mobile-menu-btn span:first-child { top: 25%; }
.mobile-menu-btn span:nth-child(2) { top: 50%; transform: translateY(-50%); }
.mobile-menu-btn span:last-child { bottom: 25%; }

.mobile-menu-btn.active span:first-child {
  top: 50%;
  transform: translateY(-50%) rotate(45deg);
}

.mobile-menu-btn.active span:nth-child(2) {
  opacity: 0;
}

.mobile-menu-btn.active span:last-child {
  bottom: 50%;
  transform: translateY(50%) rotate(-45deg);
}

/* Mobile Navigation */
@media (max-width: 1023px) {
  .mobile-menu-btn { 
    display: flex; 
  }

  nav ul {
    position: fixed;
    top: calc(3.157rem + var(--spacing-3) * 4);
    left: 0;
    z-index: var(--z-header);
    flex-direction: column;
    gap: var(--spacing-5);
    width: 100%;
    height: auto;
    max-height: calc(100vh - (3.157rem + var(--spacing-3) * 4));
    padding: var(--spacing-8);
    background: var(--background);
    opacity: 0;
    visibility: hidden;
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
  }

  nav ul.active {
    opacity: 1;
    visibility: visible;
    transition: opacity var(--transition-base), visibility var(--transition-base);
  }

  nav a.txt,
  nav a.btn {
    display: block;
    width: 100%;
    text-align: center;
  }
}

/* Header Hover Effects */
@media (hover: hover) and (pointer: fine) {
  nav a.txt:hover::after { 
    width: 100%; 
  }
  
  nav a.btn:hover {
    border-color: var(--background);
    color: var(--background);
    background: var(--text-primary);
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
  }

  .logo img:hover { 
    transform: scale(1.05); 
  }
}

/* ==========================================
   Layout Container
   ========================================== */

.container {
  width: 100%;
  max-width: 1200px;
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--spacing-3);
  padding-right: var(--spacing-3);
}

@media (min-width: 768px) {
  .container {
    padding-left: var(--spacing-6);
    padding-right: var(--spacing-6);
  }
}

@media (min-width: 1024px) {
  .container {
    padding-left: var(--spacing-8);
    padding-right: var(--spacing-8);
  }
}

@media (min-width: 1440px) {
  .container {
    padding-left: var(--spacing-10);
    padding-right: var(--spacing-10);
  }
}

/* ==========================================
   Footer Component
   ========================================== */

.minimal-footer {
  margin-top: auto;
  padding: var(--spacing-4) 0;
  border-top: var(--border-width) solid var(--overlay-light);
  background: var(--background);
}

.footer-wrapper {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-4);
  text-align: center;
}

.footer-brand {
  display: flex;
  align-items: center;
  gap: var(--spacing-3);
  font-size: var(--text-sm);
  color: var(--text-muted);
}

.footer-logo {
  width: 24px;
  height: 24px;
}

.footer-tagline {
  font-weight: var(--font-medium);
}

.footer-nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--spacing-2);
  font-size: var(--text-sm);
}

.footer-nav a {
  color: var(--text-muted);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.footer-nav a:hover {
  color: var(--primary);
}

.footer-nav .separator {
  color: var(--text-muted-50);
}

.footer-copyright {
  font-size: var(--text-xs);
  color: var(--text-muted-70);
}

@media (min-width: 768px) {
  .footer-wrapper {
    flex-direction: row;
    justify-content: space-between;
  }
  
  .footer-brand,
  .footer-nav,
  .footer-copyright {
    flex: 1;
  }
  
  .footer-nav {
    justify-content: center;
  }
  
  .footer-copyright {
    text-align: right;
  }
}

/* ==========================================
   Global Content Components
   ========================================== */

/* Content Container - now uses utility classes */
.article-content,
.content-wrapper {
  max-width: 50rem;
  margin: 0 auto;
}

.article-content > * + *,
.content-wrapper > * + * {
  margin-top: var(--spacing-6);
}

/* Section Divider */
.section-divider {
  height: var(--spacing-6);
  margin: var(--spacing-16) 0;
  box-shadow: var(--shadow-inset);
}

/* Content Boxes - simplified */
.content-box {
  /* Now uses card or card-inset utility class */
  position: relative;
  margin: var(--spacing-8) 0;
}

.content-box--highlight {
  border-left: 4px solid var(--primary);
}

.content-box--warning { border-left-color: var(--warning); }
.content-box--success { border-left-color: var(--success); }
.content-box--danger { border-left-color: var(--danger); }

/* CTA Section */
.cta-section {
  position: relative;
  margin: var(--spacing-16) 0;
  padding: var(--spacing-8);
  border-radius: var(--radius-xl);
  text-align: center;
  background: var(--background);
  box-shadow: var(--shadow-lg);
  overflow: hidden;
}

.cta-section::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--gradient-primary);
}

/* CTA Cards Grid */
.cta-cards-section {
  padding: var(--spacing-16) 0;
  background: transparent;
}

.cta-cards-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-6);
  margin: 0 auto;
}

.cta-card {
  display: flex;
  flex-direction: column;
  height: 100%;
  padding: var(--spacing-6);
  border: var(--border-width) solid var(--white-05);
  border-radius: var(--radius-xl);
  text-align: center;
  text-decoration: none !important;
  background: var(--background);
  box-shadow: var(--shadow-raised);
  transition: all var(--transition-base);
}

.cta-card h3 {
  margin-bottom: var(--spacing-4);
  font-family: var(--font-accent);
  font-size: var(--text-2xl);
  font-weight: var(--font-bold);
  color: var(--text-primary);
}

.cta-card p {
  margin-bottom: var(--spacing-6);
  font-size: var(--text-lg);
  line-height: var(--leading-relaxed);
  color: var(--text-muted);
}

.cta-card .cta-button {
  justify-content: center;
  margin-top: auto;
  padding: var(--spacing-4) var(--spacing-8);
  border: none;
  border-radius: var(--radius-md);
  font-size: var(--text-lg);
  font-weight: var(--font-semibold);
  text-decoration: none;
  color: var(--text-inverse);
  background: var(--primary);
  box-shadow: var(--shadow-md);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.cta-card .cta-button:hover {
  background: var(--primary-dark);
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

@media (min-width: 768px) {
  .cta-cards-grid {
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-8);
  }
}

@media (hover: hover) {
  .cta-card:hover {
    border-color: rgba(179, 230, 225, 0.15);
    box-shadow: var(--shadow-lg);
    transform: translateY(-2px);
  }
  
  .cta-card:hover .cta-button {
    background: var(--primary-dark);
  }
}

/* ==========================================
   Hero Section
   ========================================== */

.hero {
  margin-top: calc(var(--header-height) + var(--spacing-6));
  padding: var(--spacing-8) 0;
  text-align: center;
}

.hero-content { 
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.hero-title {
  margin-bottom: var(--spacing-4);
  font-family: var(--font-accent);
  font-size: var(--text-3xl);
  font-weight: var(--font-bold);
  line-height: var(--leading-tight);
  color: var(--text-primary);
}

.hero-subtitle {
  max-width: 600px;
  margin: 0 auto;
  font-size: var(--text-lg);
  line-height: var(--leading-relaxed);
  color: var(--text-muted);
}

/* ==========================================
   Accessibility Features
   ========================================== */

/* Screen Reader Only Content */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  border: 0;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
}

/* Skip Navigation Link */
.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  z-index: var(--z-tooltip);
  padding: var(--spacing-2) var(--spacing-4);
  border-radius: var(--radius-md);
  text-decoration: none;
  color: var(--text-inverse);
  background: var(--primary);
}

.skip-link:focus {
  top: var(--spacing-2);
}

/* Enhanced Focus Styles */
*:focus-visible {
  outline: var(--border-width-2) solid var(--primary);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

button:focus-visible,
a:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible {
  outline: var(--border-width-3) solid var(--primary);
  outline-offset: 2px;
}

/* ==========================================
   Small Screen Notice
   ========================================== */

.min-width-notice {
  display: none;
}

/* ==========================================
   Media Queries - Responsive Design
   ========================================== */

/* Very Small Screens (400px and below) */
@media (max-width: 400px) {
  html {
    font-size: clamp(14px, 3.8vw, 16px);
  }
  
  .min-width-notice {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    z-index: var(--z-tooltip);
    display: block;
    padding: var(--spacing-1) var(--spacing-2);
    border-bottom: var(--border-width) solid var(--overlay-light);
    font-size: var(--text-xs);
    text-align: center;
    color: var(--warning);
    background: var(--black-85);
  }
}

/* Tablet (768px+) */
@media (min-width: 768px) {
  .hero {
    margin-top: calc(var(--header-height) + var(--spacing-8));
  }
  
  .hero-title {
    font-size: var(--text-4xl);
  }
  
  .hero-subtitle {
    font-size: var(--text-xl);
  }
  
  .header-container {
    padding: var(--spacing-4) var(--spacing-8) var(--spacing-4) var(--spacing-4);
  }
  
  .logo img {
    height: 4.5rem;
  }
}

/* Desktop (1024px+) */
@media (min-width: 1024px) {
  .hero {
    margin-top: calc(var(--header-height) + var(--spacing-10));
  }
  
  .hero-title {
    font-size: var(--text-5xl);
  }
  
  .hero-subtitle {
    font-size: var(--text-2xl);
  }
  
  .header-container {
    padding: var(--spacing-4) var(--spacing-8);
  }
}

/* Large Desktop (1440px+) */
@media (min-width: 1440px) {
  .header-container {
    padding: var(--spacing-4) var(--spacing-10);
  }
}

/* ==========================================
   Accessibility - Motion Preferences
   ========================================== */

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* High Contrast Mode */
@media (prefers-contrast: high) {
  :root {
    --shadow-raised: 0 0 0 2px currentColor;
    --shadow-inset: inset 0 0 0 2px currentColor;
  }
}

/* ==========================================
   Print Styles
   ========================================== */

@media print {
  /* Hide Interactive Elements */
  .mobile-menu-toggle,
  .mobile-menu-btn,
  .nav-menu,
  nav,
  header,
  footer,
  .toast,
  .modal,
  .no-print,
  .action-buttons,
  .cta-section {
    display: none !important;
  }
  
  /* Reset Colors */
  body {
    color: black;
    background: white;
  }
  
  /* Add Print Borders */
  .calculator-card,
  .article-content,
  .formula-main-card,
  .cta-card,
  .content-box {
    border: var(--border-width) solid var(--color-print-border);
    box-shadow: none;
    page-break-inside: avoid;
  }
  
  /* Make Links Visible */
  a {
    text-decoration: underline;
    color: black;
  }
  
  /* Prevent Page Breaks */
  .hero,
  .section,
  h1, h2, h3, h4, h5, h6,
  ul, ol {
    page-break-inside: avoid;
  }
  
  h1, h2, h3, h4, h5, h6 {
    page-break-after: avoid;
  }
}