* {
  box-sizing: border-box;
}

body {
  background-color: #2c3e50; /* Dark blue-grey */
  display: flex;
  flex-direction: column; /* Changed to column for better layout with title and button */
  align-items: center;
  justify-content: center;
  height: 100vh;
  overflow: hidden;
  margin: 0;
  color: #ecf0f1; /* Light grey text */
}

h1 {
  margin-bottom: 30px;
}

.container {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
}

.empty {
  height: 150px;
  width: 150px;
  margin: 10px;
  border: solid 3px #3498db; /* Blue border */
  background: #ecf0f1; /* Light grey background */
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.fill {
  background-image: url('https://picsum.photos/id/237/150/150'); /* New placeholder image */
  height: 144px;
  width: 144px;
  cursor: grab;
  border-radius: 6px;
  background-size: cover;
  background-position: center;
}

.hold {
  border: solid 5px #e74c3c; /* Red border when holding */
}

.hovered {
  background-color: #34495e; /* Slightly darker blue-grey when hovered */
  border-color: #2ecc71; /* Green border when hovered */
  border-style: dashed;
}

#resetBtn {
  margin-top: 30px;
  padding: 10px 20px;
  background-color: #3498db; /* Blue button */
  color: white;
  border: none;
  border-radius: 5px;
  cursor: pointer;
  font-size: 16px;
  transition: background-color 0.3s ease;
}

#resetBtn:hover {
  background-color: #2980b9; /* Darker blue on hover */
}

@media (max-width: 800px) {
  .container {
    flex-direction: column;
  }
}