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

body {
  font-family: Arial, Helvetica, sans-serif;
  background: radial-gradient(circle at top, #222, #000);
  color: #fff;
  min-height: 100vh;
}

/* HEADER */
header {
  text-align: center;
  padding: 30px;
  font-size: 28px;
  font-weight: bold;
  letter-spacing: 2px;
}

/* CONTROLS */
.controls {
  display: flex;
  justify-content: flex-end;
  gap: 12px;
  padding: 0 40px 20px;
}

.controls input,
.controls select {
  background: #111;
  border: 1px solid #444;
  color: #fff;
  padding: 10px 14px;
  border-radius: 10px;
}

/* BACK BUTTON */
.back-top {
  position: fixed;
  top: 20px;
  left: 20px;
  padding: 8px 18px;
  background: rgba(0,0,0,0.7);
  border: 1px solid #555;
  color: #fff;
  cursor: pointer;
  display: none;
  z-index: 10;
}

/* GRID */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 30px;
  padding: 40px;
}

.card {
  background: #111;
  border: 1px solid #333;
  border-radius: 14px;
  padding: 40px 20px;
  text-align: center;
  cursor: pointer;
  transition: transform .3s, box-shadow .3s;
}

.card:hover {
  transform: translateY(-8px);
  box-shadow: 0 30px 50px rgba(0,0,0,.7);
}

/* VIEWER */
.viewer {
  display: none;
  padding: 40px;
}

.viewer img {
  width: 80vw;
  max-width: 1000px;
  display: block;
  margin: auto;
}

.engine {
  max-width: 900px;
  margin: 60px auto;
  background: #111;
  padding: 40px;
  border-radius: 16px;
  line-height: 1.9;
}