/* === Math Club - Shared Styles === */

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  background-color: #f0f4ff;
  color: #2d3748;
  min-height: 100vh;
}

/* ---- Header ---- */

header {
  background: linear-gradient(135deg, #4c6ef5, #7c3aed);
  color: white;
  text-align: center;
  padding: 2rem 1rem;
}

header h1 {
  font-size: 2.4rem;
  margin-bottom: 0.25rem;
}

header p {
  font-size: 1.15rem;
  opacity: 0.9;
}

/* ---- Main Content ---- */

main {
  max-width: 960px;
  margin: 2rem auto;
  padding: 0 1rem;
}

/* ---- Activity Card Grid (home page) ---- */

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1.5rem;
  margin-top: 1.5rem;
}

.card {
  background: white;
  border-radius: 12px;
  padding: 2rem 1.5rem;
  text-align: center;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
  transition: transform 0.2s, box-shadow 0.2s;
  text-decoration: none;
  color: inherit;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.12);
}

.card .icon {
  font-size: 3rem;
  margin-bottom: 0.75rem;
}

.card h2 {
  font-size: 1.3rem;
  margin-bottom: 0.5rem;
}

.card p {
  font-size: 0.95rem;
  color: #64748b;
  text-wrap: balance;
}

/* Card accent colors */
.card.sharing-numbers  { border-top: 4px solid #f59e0b; }
.card.cake-cutting     { border-top: 4px solid #ec4899; }
.card.four-coloring    { border-top: 4px solid #10b981; }
.card.four-color-usa   { border-top: 4px solid #06b6d4; }
.card.four-color-europe { border-top: 4px solid #06b6d4; }
.card.four-color-asia  { border-top: 4px solid #06b6d4; }
.card.four-color-africa { border-top: 4px solid #06b6d4; }
.card.four-color-north-america { border-top: 4px solid #06b6d4; }
.card.four-color-south-america { border-top: 4px solid #06b6d4; }
.card.number-bonds     { border-top: 4px solid #3b82f6; }
.card.factor-facts     { border-top: 4px solid #ec4899; }
.card.dice-bingo       { border-top: 4px solid #8b5cf6; }
.card.nim              { border-top: 4px solid #10b981; }
.card.dots-and-boxes   { border-top: 4px solid #f97316; }
.card.sequences        { border-top: 4px solid #14b8a6; }
.card.food-truck       { border-top: 4px solid #d97706; }
.card.sudoku           { border-top: 4px solid #6366f1; }

/* ---- Activity Page Layout ---- */

.activity-container {
  background: white;
  border-radius: 12px;
  padding: 2rem;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
}

.activity-container h2 {
  font-size: 1.6rem;
  margin-bottom: 1rem;
}

.activity-container .placeholder-msg {
  text-align: center;
  padding: 4rem 1rem;
  color: #94a3b8;
  font-size: 1.15rem;
}

.activity-container .placeholder-msg .icon {
  font-size: 3.5rem;
  display: block;
  margin-bottom: 1rem;
}

/* ---- Activity Title ---- */

.activity-title {
  text-align: center;
  font-size: 1.6rem;
  color: #7c3aed;
  margin-bottom: 1rem;
}

/* ---- Back Button ---- */

.back-row {
  max-width: 520px;
  margin: 0 auto 0.75rem;
  display: flex;
  align-items: center;
}

.back-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: white;
  color: #4c6ef5;
  text-decoration: none;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
  transition: transform 0.15s, box-shadow 0.15s;
}

.back-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.15);
}

/* ---- Footer ---- */

footer {
  text-align: center;
  padding: 2rem 1rem;
  color: #94a3b8;
  font-size: 0.85rem;
}