/* ============ THEME VARIABLES ============ */
:root {
  --bg: #f7f9fc;
  --text: #1a1a1a;
  --accent: #3366cc;
  --card-bg: #fff;
  --hover-filter: brightness(0.9) blur(1px);
  --scrollbar-track: #e0e0e0;
  --scrollbar-thumb: #888;
}

/* ============ BASE STYLES ============ */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
body {
  font-family: "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  padding: 1rem;
  transition: all 0.3s ease;
}
.wrapper {
  max-width: 1000px;
  margin: 0 auto;
}

/* ============ HEADER ============ */
header {
  margin-bottom: 2rem;
}
.back-button {
  text-decoration: none;
  padding: 6px 14px;
  background: var(--accent);
  color: #fff;
  border-radius: 5px;
  font-size: 0.9rem;
  display: inline-block;
  transition: background 0.3s;
}
.back-button:hover {
  background: #264eaa;
}
.challenge-title {
  font-size: 1.4rem;
  margin-top: 1rem;
}
.challenge-desc {
  font-size: 0.9rem;
  background: rgba(255, 255, 255, 0.1);
  border-left: 4px solid var(--accent);
  padding: 10px 15px;
  border-radius: 6px;
  backdrop-filter: blur(4px);
  margin-top: 10px;
}

/* ============ GALLERY ============ */
.gallery {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  padding: 20px 0;
}

.gallery img {
  width: 100%;
  aspect-ratio: 1 / 1;
  object-fit: cover;
  border-radius: 8px;
  transition: transform 0.4s ease, filter 0.4s ease;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}
.gallery img:hover {
  transform: scale(1.05);
  filter: var(--hover-filter);
}

/* ============ SCROLLBAR STYLING ============ */
body::-webkit-scrollbar {
  width: 10px;
}
body::-webkit-scrollbar-track {
  background: var(--scrollbar-track);
}
body::-webkit-scrollbar-thumb {
  background-color: var(--scrollbar-thumb);
  border-radius: 10px;
}

/* ============ RESPONSIVE ============ */
@media (max-width: 768px) {
  .gallery {
    grid-template-columns: repeat(2, 1fr);
  }
}
@media (max-width: 480px) {
  .gallery {
    grid-template-columns: 1fr;
  }
  .challenge-desc {
    font-size: 0.85rem;
  }
}