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

body {
    background: linear-gradient(to bottom, #000428, #004e92);
    font-family: 'Courier New', monospace;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    overflow: hidden;
}

#gameContainer {
    position: relative;
    border: 3px solid #00ff00;
    border-radius: 10px;
    box-shadow: 0 0 20px #00ff00;
    background: #000;
}

#gameCanvas {
    display: block;
    background: radial-gradient(ellipse at center, #001122 0%, #000000 100%);
}

#gameUI {
    position: absolute;
    top: 10px;
    left: 10px;
    right: 10px;
    display: flex;
    justify-content: space-between;
    color: #00ff00;
    font-size: 18px;
    font-weight: bold;
    text-shadow: 0 0 10px #00ff00;
    z-index: 10;
}

.screen {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.9);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    color: #00ff00;
    text-align: center;
    z-index: 20;
}

.screen.hidden {
    display: none;
}

.screen h1 {
    font-size: 48px;
    margin-bottom: 30px;
    text-shadow: 0 0 20px #00ff00;
    animation: glow 2s ease-in-out infinite alternate;
}

.screen p {
    font-size: 18px;
    margin: 10px 0;
    color: #ffffff;
}

.screen button {
    background: linear-gradient(45deg, #00ff00, #00aa00);
    border: none;
    color: #000;
    padding: 15px 30px;
    font-size: 18px;
    font-weight: bold;
    border-radius: 5px;
    cursor: pointer;
    margin-top: 20px;
    transition: all 0.3s;
    font-family: 'Courier New', monospace;
}

.screen button:hover {
    background: linear-gradient(45deg, #00aa00, #00ff00);
    box-shadow: 0 0 15px #00ff00;
    transform: scale(1.05);
}

@keyframes glow {
    from {
        text-shadow: 0 0 20px #00ff00;
    }
    to {
        text-shadow: 0 0 30px #00ff00, 0 0 40px #00ff00;
    }
}

/* Additional UI elements */
.upgrade-screen {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.9);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    color: #00ff00;
    text-align: center;
    z-index: 25;
}

.upgrade-option {
    background: rgba(255, 255, 255, 0.1);
    border: 2px solid #666;
    margin: 10px;
    padding: 15px;
    border-radius: 5px;
    cursor: pointer;
    transition: all 0.3s;
    width: 80%;
    max-width: 400px;
}

.upgrade-option.selected {
    border-color: #00ff00;
    background: rgba(0, 255, 0, 0.2);
    box-shadow: 0 0 15px rgba(0, 255, 0, 0.5);
}

.upgrade-option h3 {
    margin: 0 0 10px 0;
    color: #00ff00;
    font-size: 18px;
}

.upgrade-option p {
    margin: 0;
    color: #cccccc;
    font-size: 14px;
}

/* Game stats display */
.stats-display {
    position: absolute;
    top: 50px;
    left: 10px;
    color: #00ff00;
    font-size: 12px;
    background: rgba(0, 0, 0, 0.7);
    padding: 10px;
    border-radius: 5px;
    border: 1px solid #00ff00;
}

.stats-display div {
    margin: 2px 0;
}

/* Enhanced visual effects */
@keyframes pulse {
    0% { opacity: 1; }
    50% { opacity: 0.7; }
    100% { opacity: 1; }
}

.pulsing {
    animation: pulse 1s infinite;
}

/* Pixel art styling */
canvas {
    image-rendering: -moz-crisp-edges;
    image-rendering: -webkit-crisp-edges;
    image-rendering: pixelated;
    image-rendering: crisp-edges;
}

/* Responsive design */
@media (max-width: 900px) {
    #gameCanvas {
        width: 90vw;
        height: 67.5vw;
    }
    
    #gameContainer {
        width: 90vw;
    }
    
    .screen h1 {
        font-size: 36px;
    }
    
    .screen p {
        font-size: 16px;
    }
    
    #gameUI {
        font-size: 16px;
    }
    
    .upgrade-option {
        width: 90%;
    }
    
    .stats-display {
        font-size: 10px;
        padding: 5px;
    }
}