/* Theme variables */
:root {
  --bg: #f0f4f8;
  --card-bg: #fff;
  --text: #333;
  --accent: #007bff;
  --button-hover: #0056b3;
  --shadow: rgba(0,0,0,0.1);
}
body.dark {
  --bg: #121212;
  --card-bg: #1e1e1e;
  --text: #e0e0e0;
  --accent: #4f8cff;
  --button-hover: #3a6fd9;
  --shadow: rgba(0,0,0,0.5);
}

/* Reset & Base */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
body {
  background: var(--bg);
  color: var(--text);
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  line-height: 1.6;
  padding: 40px 20px;
  transition: background 0.4s ease, color 0.4s ease;
}
.container {
  max-width: 1200px;
  margin: 0 auto;
  text-align: center;
}

/* Challenge Box */
.challenge-box {
  background: var(--card-bg);
  padding: 30px 20px;
  border-radius: 12px;
  margin-bottom: 40px;
  box-shadow: 0 4px 12px var(--shadow);
  transition: background 0.4s ease;
}
.challenge-box h1 {
  font-size: 1.8rem;
  margin-bottom: 10px;
}
.challenge-box p {
  font-size: 1.1rem;
  margin-bottom: 20px;
}
.toggle-mode {
  background: var(--accent);
  color: #fff;
  padding: 10px 16px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background 0.3s;
}
.toggle-mode:hover {
  background: var(--button-hover);
}

/* Pricing Table */
.pricing-table {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 24px;
}
.plan {
  background: var(--card-bg);
  border-radius: 16px;
  padding: 30px 20px;
  width: 280px;
  box-shadow: 0 10px 20px var(--shadow);
  transition: transform 0.4s ease, box-shadow 0.4s ease, background 0.4s ease;
}
.plan:hover {
  transform: translateY(-8px);
  box-shadow: 0 16px 32px var(--shadow);
}
.plan h2 {
  font-size: 1.5rem;
  margin-bottom: 10px;
}
.price {
  font-size: 1.3rem;
  font-weight: bold;
  color: var(--accent);
  margin-bottom: 20px;
}
.plan ul {
  list-style: none;
  margin-bottom: 20px;
}
.plan li {
  margin: 8px 0;
}
.plan button {
  padding: 10px 20px;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background 0.3s;
}
.plan button:hover {
  background: var(--button-hover);
}

/* Featured Plan */
.plan.featured {
  transform: scale(1.05);
  background: linear-gradient(to bottom right, var(--accent), var(--button-hover));
  color: white;
}
.plan.featured h2,
.plan.featured .price,
.plan.featured li {
  color: white;
}
.plan.featured button {
  background: #fff;
  color: var(--accent);
}
.plan.featured button:hover {
  background: #f1f1f1;
}

/* Back Button */
.back-button {
  display: inline-block;
  margin-top: 40px;
  text-decoration: none;
  font-weight: 500;
  color: var(--accent);
  padding: 10px 16px;
  border: 1px solid var(--accent);
  border-radius: 6px;
  transition: background 0.3s, color 0.3s;
}
.back-button:hover {
  background: var(--accent);
  color: white;
}

/* Responsive */
@media (max-width: 900px) {
  .pricing-table {
    flex-direction: column;
    align-items: center;
  }
}