/* ===== SOLUTION STACK SECTION ===== */

.solution-stack-section {
  position: relative;
  height: 280vh;
  background:
    radial-gradient(circle at top, rgba(59, 130, 246, 0.06), transparent 35%),
    linear-gradient(180deg, #f8fafc 0%, #eef4fb 100%);
  padding: 90px 0;
  overflow: clip;
}

.solution-stack-section::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(circle at 20% 20%, rgba(255, 122, 0, 0.05), transparent 12%),
    radial-gradient(circle at 80% 75%, rgba(31, 60, 136, 0.05), transparent 18%);
  pointer-events: none;
}

.solution-stack-stage {
  position: relative;
  height: 100%;
}

.solution-stack-sticky {
  position: sticky;
  top: 110px;
  height: calc(100vh - 110px);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-start;
}

/* ===== HEADER ===== */

.solution-stack-sticky .section-head {
  text-align: center;
  max-width: 760px;
  margin-bottom: 32px;
  position: relative;
  z-index: 3;
}

.solution-stack-sticky .section-tag {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 18px;
  border-radius: 999px;
  border: 1px solid rgba(31, 60, 136, 0.12);
  background: rgba(255,255,255,0.72);
  color: #1f3c88;
  font-size: 13px;
  font-weight: 700;
  margin-bottom: 14px;
  backdrop-filter: blur(8px);
}

.solution-stack-sticky h2 {
  font-size: 58px;
  font-weight: 800;
  line-height: 1.02;
  letter-spacing: -0.04em;
  margin-bottom: 14px;
  color: #0f172a;
}

.solution-stack-sticky p {
  color: #64748b;
  font-size: 18px;
  line-height: 1.8;
}

/* ===== GRID ===== */

.solution-groups-grid {
  position: relative;
  width: 100%;
  max-width: 920px;
  height: 760px;
  perspective: 1200px;
}

/* ===== CARDS ===== */

.solution-group-card {
  position: absolute;
  left: 50%;
  top: 0;
  width: 100%;
  max-width: 760px;
  transform: translateX(-50%);
  border-radius: 28px;
  overflow: hidden;
  color: #fff;
  box-shadow:
    0 22px 50px rgba(15, 23, 42, 0.08),
    0 0 0 1px rgba(255,255,255,0.08) inset;
  transition:
    transform 0.2s linear,
    opacity 0.2s linear,
    filter 0.2s linear,
    box-shadow 0.3s ease;
  will-change: transform, opacity, filter;
  transform-style: preserve-3d;
  backface-visibility: hidden;
}

.solution-group-card::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    linear-gradient(180deg, rgba(255,255,255,0.10), transparent 18%),
    radial-gradient(circle at top right, rgba(255,255,255,0.10), transparent 20%);
  pointer-events: none;
}

.solution-group-card.is-active {
  box-shadow:
    0 30px 80px rgba(15, 23, 42, 0.16),
    0 0 30px rgba(59,130,246,0.08);
}

.solution-group-card:nth-child(1){ z-index: 3; }
.solution-group-card:nth-child(2){ z-index: 2; }
.solution-group-card:nth-child(3){ z-index: 1; }

/* ===== CARD HEADER ===== */

.solution-group-head {
  padding: 28px 30px 18px;
  text-align: center;
}

.solution-group-head h3 {
  font-size: 38px;
  font-weight: 800;
  line-height: 1.05;
  margin-bottom: 8px;
  color: #fff;
  text-shadow: 0 2px 10px rgba(0,0,0,0.08);
}

.solution-group-head p {
  font-size: 14px;
  line-height: 1.6;
  opacity: 0.95;
  color: rgba(255,255,255,0.92);
  margin: 0;
}

/* ===== LIST ===== */

.solution-group-list {
  padding: 6px 18px 20px;
}

.solution-group-item {
  display: grid;
  grid-template-columns: 18px 1fr auto;
  gap: 12px;
  align-items: center;
  padding: 14px 16px;
  border-top: 1px solid rgba(255,255,255,0.18);
  font-size: 15px;
}

.solution-item-bullet {
  font-size: 18px;
  line-height: 1;
  color: rgba(255,255,255,0.92);
}

.solution-item-title {
  font-weight: 600;
  color: #fff;
}

.solution-item-link {
  color: #fff;
  text-decoration: none;
  font-size: 13px;
  font-weight: 700;
  white-space: nowrap;
  opacity: 0.95;
  transition: transform 0.25s ease, opacity 0.25s ease;
}

.solution-item-link::after {
  content: " →";
}

.solution-item-link:hover {
  transform: translateX(3px);
  opacity: 1;
}

.solution-item-link.disabled {
  opacity: 0.55;
  pointer-events: none;
}

/* ===== THEMES ===== */

.theme-red {
  background: linear-gradient(135deg, #de0e47 0%, #bf0e3c 100%);
}

.theme-blue {
  background: linear-gradient(135deg, #1a7db8 0%, #135f94 100%);
}

.theme-indigo {
  background: linear-gradient(135deg, #3a4be2 0%, #2b3cc0 100%);
}

.theme-green {
  background: linear-gradient(135deg, #27ae60 0%, #229954 100%);
}

.theme-orange {
  background: linear-gradient(135deg, #e67e22 0%, #d35400 100%);
}

/* ===== MOBILE ===== */

@media (max-width: 768px) {
  .solution-stack-section {
    height: auto;
    padding: 70px 0;
  }

  .solution-stack-sticky {
    position: relative;
    top: auto;
    height: auto;
  }

  .solution-groups-grid {
    height: auto;
    display: flex;
    flex-direction: column;
    gap: 18px;
    perspective: none;
  }

  .solution-group-card {
    position: relative;
    transform: none !important;
    left: auto;
    top: auto;
    max-width: 100%;
    filter: none !important;
    opacity: 1 !important;
  }

  .solution-stack-sticky h2 {
    font-size: 40px;
  }

  .solution-group-head h3 {
    font-size: 26px;
  }

  .solution-group-item {
    grid-template-columns: 16px 1fr;
  }

  .solution-item-link {
    grid-column: 2 / 3;
    margin-top: 6px;
  }
}

.solution-group-card.is-active {
  box-shadow:
    0 34px 90px rgba(15, 23, 42, 0.18),
    0 0 30px rgba(59,130,246,0.08);
}

.solution-group-card {
  transform-origin: center top;
}