:root {
    --bg-color: #222;
    --text-color: #fff;
    --primary-color: #4a90e2;
    --secondary-color: #e74c3c;
    --font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    margin: 0;
    padding: 0;
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: var(--font-family);
    overflow: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
}

#game-container {
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
}

#ui-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none; /* Let clicks pass through to canvas when not interacting with UI */
}

.screen {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    background-color: rgba(0, 0, 0, 0.8);
    pointer-events: auto; /* Re-enable clicks for menus */
    transition: opacity 0.3s ease;
}

.hidden {
    opacity: 0;
    pointer-events: none;
    display: none; /* Actually hide it so it doesn't block clicks if opacity is 0 */
}

h1, h2 {
    margin-bottom: 20px;
    text-transform: uppercase;
    letter-spacing: 2px;
}

button {
    padding: 10px 20px;
    margin: 10px;
    font-size: 1.2rem;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: transform 0.1s, background-color 0.2s;
}

button:hover {
    background-color: #357abd;
    transform: scale(1.05);
}

button:active {
    transform: scale(0.95);
}

#hud {
    background: none;
    justify-content: space-between;
    align-items: flex-start;
    padding: 20px;
    flex-direction: row;
    height: auto;
    pointer-events: none;
}

#hud button {
    pointer-events: auto;
    margin: 0;
    padding: 5px 15px;
    font-size: 1rem;
}

.hud-top {
    font-size: 1.5rem;
    font-weight: bold;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.5);
}

#levels-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 15px;
    margin-bottom: 20px;
}

.level-btn {
    width: 60px;
    height: 60px;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #333;
    border: 2px solid var(--primary-color);
}

.level-btn.locked {
    opacity: 0.5;
    cursor: not-allowed;
    background-color: #111;
    border-color: #555;
}

/* Light mode overrides */
body.light-mode {
    --bg-color: #f0f0f0;
    --text-color: #333;
}

body.light-mode .screen {
    background-color: rgba(255, 255, 255, 0.8);
}