/* ===================================
   CSS Custom Properties (Variables)
   =================================== */
:root {
  /* Colors */
  --bg: #f6f4f2;
  --surface: #ffffff;
  --text: #263238;
  --muted: #6b6b6b;
  --accent: #1976a5;
  --accent-2: #ffb74d;
  --accent-hover: #145a7d;
  --border: #e0e0e0;
  --shadow: rgba(0, 0, 0, 0.1);
  --shadow-lg: rgba(0, 0, 0, 0.15);

  /* Spacing (8px base unit) */
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-6: 48px;
  --space-8: 64px;

  /* Layout */
  --max-width: 1280px;
  --header-height: 72px;

  /* Typography */
  --font-base: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;

  /* Transitions - Using transform and opacity for better performance */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-base);
  font-size: 16px;
  line-height: 1.6;
  color: var(--text);
  background-color: var(--bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

a {
  color: inherit;
  text-decoration: none;
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
}

ul {
  list-style: none;
}

/* Skip link for keyboard accessibility */
.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  background: var(--accent);
  color: var(--surface);
  padding: var(--space-1) var(--space-2);
  text-decoration: none;
  font-weight: 600;
  z-index: 10000;
  border-radius: 0 0 4px 0;
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: 0;
}

/* ===================================
   Layout Utilities
   =================================== */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-2);
}

@media (min-width: 768px) {
  .container {
    padding: 0 var(--space-4);
  }
}

/* ===================================
   Header & Navigation
   =================================== */
.header {
  position: sticky;
  top: 0;
  background: var(--text);
  color: var(--surface);
  height: var(--header-height);
  z-index: 1000;
  box-shadow: 0 2px 8px var(--shadow);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.nav__logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--surface);
}

.nav__toggle {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: var(--space-1);
  z-index: 1001;
}

.nav__toggle-icon,
.nav__toggle-icon::before,
.nav__toggle-icon::after {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--surface);
  transition: transform var(--transition-base), opacity var(--transition-base);
}

.nav__toggle-icon::before,
.nav__toggle-icon::after {
  content: "";
}

.nav__toggle[aria-expanded="true"] .nav__toggle-icon {
  transform: rotate(45deg);
}

.nav__toggle[aria-expanded="true"] .nav__toggle-icon::before {
  transform: translateY(6px) rotate(90deg);
}

.nav__toggle[aria-expanded="true"] .nav__toggle-icon::after {
  opacity: 0;
}

.nav__menu {
  position: fixed;
  top: var(--header-height);
  left: 0;
  right: 0;
  background: var(--text);
  padding: var(--space-3);
  transform: translateY(-100%);
  opacity: 0;
  transition: transform var(--transition-base), opacity var(--transition-base);
  pointer-events: none;
}

.nav__menu.active {
  transform: translateY(0);
  opacity: 1;
  pointer-events: auto;
}

.nav__menu li {
  margin-bottom: var(--space-2);
}

.nav__link {
  display: block;
  padding: var(--space-2);
  color: var(--surface);
  font-weight: 500;
  transition: opacity var(--transition-fast);
}

.nav__link:hover,
.nav__link:focus {
  opacity: 0.8;
}

.nav__link.active {
  color: var(--accent-2);
}

@media (min-width: 768px) {
  .nav__toggle {
    display: none;
  }

  .nav__menu {
    position: static;
    display: flex;
    gap: var(--space-1);
    padding: 0;
    transform: none;
    opacity: 1;
    pointer-events: auto;
  }

  .nav__menu li {
    margin-bottom: 0;
  }

  .nav__link {
    padding: var(--space-1) var(--space-2);
  }
}

/* ===================================
   Buttons
   =================================== */
.btn {
  display: inline-block;
  padding: var(--space-2) var(--space-4);
  font-size: 1rem;
  font-weight: 600;
  text-align: center;
  border-radius: 4px;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), opacity var(--transition-fast);
  box-shadow: 0 2px 4px var(--shadow);
}

.btn:hover,
.btn:focus {
  transform: translateY(-2px);
  box-shadow: 0 4px 8px var(--shadow-lg);
}

.btn:active {
  transform: translateY(0);
}

.btn--primary {
  background: var(--accent);
  color: var(--surface);
}

.btn--primary:hover {
  background: var(--accent-hover);
}

.btn--secondary {
  background: var(--accent-2);
  color: var(--text);
}

.btn--secondary:hover {
  opacity: 0.9;
}

.btn--outline {
  background: transparent;
  color: var(--accent);
  border: 2px solid var(--accent);
}

.btn--outline:hover {
  background: var(--accent);
  color: var(--surface);
}

/* ===================================
   Sections
   =================================== */
.section {
  padding: var(--space-6) 0;
}

.section--alt {
  background: var(--surface);
}

.section__header {
  text-align: center;
  margin-bottom: var(--space-6);
}

.section__title {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: var(--space-2);
  color: var(--text);
}

.section__subtitle {
  font-size: 1.125rem;
  color: var(--muted);
  max-width: 600px;
  margin: 0 auto;
}

.section__cta {
  text-align: center;
  margin-top: var(--space-6);
}

@media (min-width: 768px) {
  .section {
    padding: var(--space-8) 0;
  }

  .section__title {
    font-size: 2.5rem;
  }
}

/* ===================================
   Footer
   =================================== */
.footer {
  background: var(--text);
  color: var(--surface);
  padding: var(--space-6) 0 var(--space-3);
}

.footer__content {
  display: grid;
  gap: var(--space-4);
  grid-template-columns: 1fr;
  margin-bottom: var(--space-4);
}

@media (min-width: 768px) {
  .footer__content {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .footer__content {
    grid-template-columns: repeat(4, 1fr);
  }
}

.footer__title {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: var(--space-2);
}

.footer__text {
  line-height: 1.6;
  opacity: 0.9;
  margin-bottom: var(--space-2);
}

.footer__social {
  display: flex;
  gap: var(--space-2);
}

.footer__social-link {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  background: rgba(255, 255, 255, 0.1);
  border-radius: 50%;
  transition: opacity var(--transition-fast), background-color var(--transition-fast);
}

.footer__social-link:hover {
  background: var(--accent);
  opacity: 1;
}

.footer__heading {
  font-size: 1.125rem;
  font-weight: 600;
  margin-bottom: var(--space-2);
}

.footer__links {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.footer__links a {
  opacity: 0.9;
  transition: opacity var(--transition-fast);
}

.footer__links a:hover {
  opacity: 1;
  color: var(--accent-2);
}

.footer__bottom {
  text-align: center;
  padding-top: var(--space-3);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  opacity: 0.8;
}

/* ===================================
   Modal
   =================================== */
.modal {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.8);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 2000;
  padding: var(--space-2);
  opacity: 0;
  transition: opacity var(--transition-base);
  pointer-events: none;
}

.modal.active {
  opacity: 1;
  pointer-events: auto;
}

.modal__content {
  background: var(--surface);
  border-radius: 8px;
  max-width: 800px;
  max-height: 90vh;
  overflow-y: auto;
  position: relative;
  transform: scale(0.9);
  transition: transform var(--transition-base);
}

.modal.active .modal__content {
  transform: scale(1);
}

.modal__close {
  position: sticky;
  top: 0;
  right: 0;
  float: right;
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--text);
  color: var(--surface);
  border-radius: 50%;
  margin: var(--space-2);
  font-size: 1.5rem;
  z-index: 1;
  transition: opacity var(--transition-fast);
}

.modal__close:hover {
  opacity: 0.8;
}

/* ===================================
   Utility Classes
   =================================== */
.mt-1 {
  margin-top: var(--space-1);
}
.mt-2 {
  margin-top: var(--space-2);
}
.mt-3 {
  margin-top: var(--space-3);
}
.mt-4 {
  margin-top: var(--space-4);
}

.mb-1 {
  margin-bottom: var(--space-1);
}
.mb-2 {
  margin-bottom: var(--space-2);
}
.mb-3 {
  margin-bottom: var(--space-3);
}
.mb-4 {
  margin-bottom: var(--space-4);
}

.p-1 {
  padding: var(--space-1);
}
.p-2 {
  padding: var(--space-2);
}
.p-3 {
  padding: var(--space-3);
}
.p-4 {
  padding: var(--space-4);
}

.text-center {
  text-align: center;
}
.text-muted {
  color: var(--muted);
}

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