/* =========================================================
   layout.css - Layout system (CLEANED & REFACTORED)
   
   Section Organization:
   - Header & Navigation System (header, logo, nav-toggle, nav)
   - Section & Content (sections, grids, problem lists)
   - Animations (reveal, transitions)
   - Footer & Metadata
   - Responsive Rules
   ========================================================= */


/* ================= CONTAINER ================= */

.container,
.mid {
  width: 100%;
  margin: 0 auto;
  padding-left: var(--container-padding-mobile);
  padding-right: var(--container-padding-mobile);
  box-sizing: border-box;
}

.container {
  max-width: 1200px;
}

.mid {
  max-width: 900px;
}


/* ================= HEADER & NAVIGATION SYSTEM ================= */

.header {
  position: sticky;
  top: 0;
  z-index: 1000;
  width: 100vw;
  max-width: 100vw;
  margin-left: calc(50% - 50vw);
  margin-right: calc(50% - 50vw);
  padding: 0;
  overflow: visible;
  transition: background var(--transition), box-shadow var(--transition), border-color var(--transition);
}

.header.transparent {
  background: transparent;
  border-bottom: none;
  box-shadow: none;
}

.header.scrolled {
  background: var(--bg-light);
  border-bottom: 1px solid var(--border);
  box-shadow: 0 6px 24px rgba(0, 0, 0, 0.08);
  backdrop-filter: blur(4px);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--spacing-md);
  min-height: 72px;
  width: 100%;
  padding: 0 var(--container-padding-mobile);
}

.header .logo {
  position: absolute;
  left: var(--container-padding-mobile);
  top: 50%;
  transform: translateY(-50%);
  font-size: clamp(1.05rem, 4.2vw, 1.25rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--primary);
  text-decoration: none;
  white-space: nowrap;
  z-index: 1010;
}

.header .nav-toggle {
  position: absolute;
  right: var(--container-padding-mobile);
  top: 50%;
  transform: translateY(-50%);
  min-width: 44px;
  min-height: 44px;
  z-index: 1010;
}

.nav {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
  position: fixed;
  top: 72px;
  left: 0;
  right: 0;
  background: var(--bg-light);
  padding: var(--spacing-md) 0;
  box-shadow: var(--shadow-sm);
  opacity: 0;
  visibility: hidden;
  transform: translateY(-10px);
  transition: opacity var(--menu-transition), visibility var(--menu-transition), transform var(--menu-transition);
  z-index: 999;
}

.nav.active {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.nav a {
  position: relative;
  display: flex;
  align-items: center;
  padding: 0.9rem var(--spacing-md);
  min-height: 48px;
  font-weight: 500;
  color: var(--text-dark);
  white-space: nowrap;
  transition: background var(--transition), color var(--transition);
}

.nav a:hover,
.nav a.active {
  color: var(--primary);
  background: var(--bg-soft);
}

.nav a.active::after {
  content: "";
  position: absolute;
  inset: 0 auto 0 0;
  width: 4px;
  background: var(--primary);
  border-radius: 0 2px 2px 0;
}


/* ================= SECTION & CONTENT ================= */

.section {
  padding: var(--section-padding-mobile) 0;
  background: transparent;
}

.section h1,
.section h2 {
  text-align: center;
  margin-bottom: var(--spacing-lg);
}

.section h2 {
  max-width: 820px;
  margin-left: auto;
  margin-right: auto;
}

.problem-list {
  max-width: 720px;
  margin: 0 auto;
  padding-left: 1.25rem;
  text-align: left;
  color: var(--text-dark);
  line-height: 1.6;
}

.problem-list li {
  margin-bottom: var(--spacing-sm);
}

.grid-2cols {
  display: grid;
  gap: var(--spacing-xl);
  grid-template-columns: 1fr;
}


/* ================= ANIMATIONS ================= */

.reveal {
  opacity: 0;
  transform: translateY(30px);
  will-change: transform, opacity;
}

.reveal.in-view {
  opacity: 1;
  transform: translateY(0);
  transition: opacity 0.6s ease, transform 0.6s ease;
}


/* ================= FOOTER ================= */

.footer {
  width: 100vw;
  max-width: 100vw;
  margin-left: calc(50% - 50vw);
  margin-right: calc(50% - 50vw);
  margin-top: var(--spacing-3xl);
  background: var(--bg-light);
  border-top: 1px solid var(--border);
  text-align: center;
  position: relative;
  overflow: visible;
  padding: 0 !important;
}

.footer-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-lg);
  padding: calc(var(--section-padding-mobile) + 1.5rem) var(--container-padding-mobile);
}

.footer-brand strong {
  font-size: 1.1rem;
  color: var(--primary);
}

.footer-brand p {
  margin-top: var(--spacing-sm);
  font-size: 0.9rem;
  color: var(--text-soft);
}

.footer-contact {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
  gap: var(--spacing-md);
}

.footer-contact a {
  font-size: 0.9rem;
  color: var(--text-dark);
  transition: color var(--transition);
}

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

.footer-copy {
  margin-top: var(--spacing-md);
  font-size: 0.8rem;
  color: var(--text-soft);
}


/* ================= RESPONSIVE ================= */

@media (min-width: var(--bp-xl)) {
  .footer {
    padding: var(--spacing-3xl) 0;
  }

  .footer-inner {
    gap: var(--spacing-2xl);
  }
}