body, html {
    height: 100%;
    margin: 0;
    padding: 0;
    background-color: #222;
    font-family: 'Courier New', Courier, monospace;
    overflow: hidden;
    color: white;
}

#gameCanvas {
    display: block;
    width: 100%;
    height: 100%;
    background-color: #333;
}

#ui-layer {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    padding: 20px;
    box-sizing: border-box;
}

#top-bar, #bottom-bar {
    pointer-events: auto;
    background-color: rgba(0, 0, 0, 0.85);
    padding: 15px;
    border-radius: 8px;
    display: flex;
    gap: 20px;
    align-items: center;
}

#top-bar {
    align-self: flex-start;
    font-size: 18px;
    font-weight: bold;
    border: 1px solid #555;
}

#bottom-bar {
    align-self: center;
    width: 100%;
    justify-content: center;
    border-top: 2px solid #444;
    flex-wrap: wrap;
}

.upgrade-container {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    justify-content: center;
}

button {
    background-color: #4CAF50;
    border: none;
    color: white;
    padding: 10px 15px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 14px;
    cursor: pointer;
    border-radius: 4px;
    font-family: inherit;
    transition: background-color 0.2s;
    border-bottom: 3px solid #3e8e41;
}

button:hover {
    background-color: #45a049;
}

button:active {
    border-bottom: 1px solid #3e8e41;
    transform: translateY(2px);
}

button:disabled {
    background-color: #555;
    border-bottom: 3px solid #333;
    cursor: not-allowed;
    opacity: 0.6;
}

#toggleBtn {
    background-color: #2196F3;
    border-bottom-color: #0b7dda;
    font-weight: bold;
    margin-right: 20px;
}