body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    background-color: #f0f2f5;
    color: #333;
}

h1 {
    color: #1a2b4d;
}

.game-container {
    margin: 20px;
}

#puzzle-board {
    display: grid;
    grid-template-columns: repeat(3, 100px);
    grid-template-rows: repeat(3, 100px);
    border: 3px solid #333;
    background-color: #fdfdfd;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

.tile {
    width: 100px;
    height: 100px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2.5rem;
    font-weight: bold;
    color: #fff;
    background-color: #4a77d4;
    border: 1px solid #fff;
    box-sizing: border-box; /* Important for grid */
    cursor: pointer;
    transition: background-color 0.2s;
}

.tile:hover {
    background-color: #6a93f4;
}

.tile.empty {
    background-color: #fdfdfd;
    cursor: default;
    box-shadow: inset 0 0 10px rgba(0,0,0,0.1);
}

.controls button {
    font-size: 1rem;
    padding: 10px 20px;
    margin: 0 10px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    background-color: #007bff;
    color: white;
    transition: background-color 0.2s;
}

.controls button:hover {
    background-color: #0056b3;
}

#solve-btn {
    background-color: #28a745;
}
#solve-btn:hover {
    background-color: #218838;
}
#solve-btn:disabled {
    background-color: #999;
    cursor: not-allowed;
}

#status-message {
    margin-top: 20px;
    font-size: 1.2rem;
    font-weight: bold;
    color: #28a745;
}

/* Style for the 'Back to Main Menu' link */
.back-link {
    display: inline-block;
    margin-bottom: 20px;
    font-size: 1rem;
    color: #007bff;
    text-decoration: none;
}
.back-link:hover {
    text-decoration: underline;
}