/* CSS Reset và Cài đặt cơ bản */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html, body {
    height: 100%;
    width: 100%;
    overflow: hidden;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Container chính của game */
#game-container {
    position: relative;
    width: 100%;
    height: 100%;
    background: #000000;
    display: flex;
    justify-content: center;
    align-items: center;
    /* Tắt tính năng chọn văn bản */
    user-select: none;
    -webkit-user-select: none;
    -ms-user-select: none;
    -moz-user-select: none;
    /* Tắt highlight khi tap trên mobile */
    -webkit-tap-highlight-color: transparent;
    overflow: hidden;
}

/* Space Background */
#space-background {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 0;
    pointer-events: none;
}

/* Stars */
.stars {
    position: absolute;
    width: 100%;
    height: 100%;
    background-image: 
        radial-gradient(2px 2px at 20% 30%, white, transparent),
        radial-gradient(2px 2px at 60% 70%, white, transparent),
        radial-gradient(1px 1px at 50% 50%, white, transparent),
        radial-gradient(1px 1px at 80% 10%, white, transparent),
        radial-gradient(2px 2px at 90% 40%, white, transparent),
        radial-gradient(1px 1px at 33% 60%, white, transparent),
        radial-gradient(1px 1px at 10% 80%, white, transparent),
        radial-gradient(2px 2px at 40% 20%, white, transparent),
        radial-gradient(1px 1px at 70% 90%, white, transparent),
        radial-gradient(1px 1px at 15% 50%, white, transparent),
        radial-gradient(2px 2px at 85% 60%, white, transparent),
        radial-gradient(1px 1px at 25% 15%, white, transparent),
        radial-gradient(1px 1px at 55% 85%, white, transparent),
        radial-gradient(2px 2px at 75% 25%, white, transparent),
        radial-gradient(1px 1px at 45% 75%, white, transparent),
        radial-gradient(1px 1px at 5% 20%, white, transparent),
        radial-gradient(2px 2px at 95% 80%, white, transparent),
        radial-gradient(1px 1px at 65% 40%, white, transparent),
        radial-gradient(1px 1px at 35% 90%, white, transparent),
        radial-gradient(2px 2px at 12% 45%, white, transparent),
        radial-gradient(1px 1px at 88% 25%, white, transparent),
        radial-gradient(1px 1px at 72% 65%, white, transparent),
        radial-gradient(2px 2px at 28% 75%, white, transparent),
        radial-gradient(1px 1px at 55% 10%, white, transparent),
        radial-gradient(1px 1px at 18% 60%, white, transparent),
        radial-gradient(2px 2px at 82% 50%, white, transparent),
        radial-gradient(1px 1px at 45% 35%, white, transparent),
        radial-gradient(1px 1px at 95% 15%, white, transparent),
        radial-gradient(2px 2px at 8% 85%, white, transparent),
        radial-gradient(1px 1px at 62% 20%, white, transparent);
    background-repeat: repeat;
    background-size: 300px 300px;
    animation: twinkle 4s ease-in-out infinite alternate;
}

@keyframes twinkle {
    0% { opacity: 0.5; }
    100% { opacity: 1; }
}

/* Planets */
.planets {
    position: absolute;
    width: 100%;
    height: 100%;
}

.planet {
    position: absolute;
    border-radius: 50%;
    opacity: 0.6;
    animation: float 20s ease-in-out infinite;
}

.planet-1 {
    width: 80px;
    height: 80px;
    background: radial-gradient(circle at 30% 30%, #4a90e2, #2c5282);
    top: 15%;
    left: 10%;
    box-shadow: 0 0 20px rgba(74, 144, 226, 0.5);
    animation-duration: 25s;
}

.planet-2 {
    width: 60px;
    height: 60px;
    background: radial-gradient(circle at 30% 30%, #e74c3c, #8b2635);
    top: 70%;
    right: 15%;
    box-shadow: 0 0 15px rgba(231, 76, 60, 0.5);
    animation-duration: 30s;
    animation-delay: -5s;
}

.planet-3 {
    width: 40px;
    height: 40px;
    background: radial-gradient(circle at 30% 30%, #f39c12, #b87333);
    top: 40%;
    right: 5%;
    box-shadow: 0 0 10px rgba(243, 156, 18, 0.5);
    animation-duration: 35s;
    animation-delay: -10s;
}

@keyframes float {
    0%, 100% { transform: translate(0, 0) rotate(0deg); }
    25% { transform: translate(10px, -10px) rotate(5deg); }
    50% { transform: translate(-5px, 5px) rotate(-5deg); }
    75% { transform: translate(5px, 10px) rotate(3deg); }
}

/* SVG canvas, nơi render game */
#game-svg {
    width: 100%;
    height: 100%;
    max-width: 450px; /* Giới hạn chiều rộng trên desktop */
    cursor: pointer;
    position: relative;
    z-index: 1;
}

/* Hiển thị UI (Điểm số, Combo) */
#ui-container {
    position: absolute;
    top: 20px;
    left: 0;
    width: 100%;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    color: white;
    font-size: 24px;
    font-weight: 600;
    text-shadow: 0 2px 8px rgba(255, 255, 255, 0.3), 0 0 10px rgba(255, 255, 255, 0.2);
    pointer-events: none; /* Cho phép click xuyên qua UI */
    z-index: 2;
}

#score-best {
    text-align: right;
}

/* Hiển thị combo "Perfect" */
#combo-display {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 48px;
    font-weight: bold;
    color: #ffffff;
    text-shadow: 0 0 10px #ff0, 0 0 20px #ff0;
    opacity: 0;
    transition: opacity 0.5s ease-out, transform 0.5s ease-out;
    pointer-events: none;
    z-index: 10;
}

#combo-display.show {
    opacity: 1;
    transform: translate(-50%, -100%) scale(1.2);
}

/* Màn hình Game Over */
#game-over-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.7);
    display: none; /* Ẩn ban đầu */
    flex-direction: column;
    justify-content: center;
    align-items: center;
    color: white;
    z-index: 20;
    opacity: 0;
    transition: opacity 0.3s ease;
}

#game-over-overlay.show {
    display: flex;
    opacity: 1;
}

#game-over-overlay h2 {
    font-size: 48px;
    font-weight: bold;
    margin-bottom: 10px;
    text-shadow: 0 4px 6px rgba(0,0,0,0.3);
}

#final-score {
    font-size: 24px;
    margin-bottom: 30px;
}

#restart-button {
    padding: 15px 30px;
    font-size: 20px;
    font-weight: 600;
    color: #5f76e8;
    background-color: white;
    border: none;
    border-radius: 50px;
    cursor: pointer;
    box-shadow: 0 5px 15px rgba(0,0,0,0.2);
    transition: transform 0.1s ease, box-shadow 0.1s ease;
}

#restart-button:active {
    transform: scale(0.95);
    box-shadow: 0 2px 10px rgba(0,0,0,0.2);
}

/* Nút bật/tắt âm thanh */
#sound-toggle {
    position: absolute;
    bottom: 20px;
    right: 20px;
    width: 50px;
    height: 50px;
    background-color: rgba(255, 255, 255, 0.15);
    border: 2px solid rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 0 15px rgba(255, 255, 255, 0.2), inset 0 0 10px rgba(255, 255, 255, 0.1);
    transition: transform 0.1s ease, box-shadow 0.1s ease, background-color 0.2s ease, border-color 0.2s ease;
    pointer-events: auto;
    z-index: 15;
    backdrop-filter: blur(5px);
}

#sound-toggle:hover {
    background-color: rgba(255, 255, 255, 0.25);
    border-color: rgba(255, 255, 255, 0.5);
    transform: scale(1.05);
    box-shadow: 0 0 20px rgba(255, 255, 255, 0.3), inset 0 0 15px rgba(255, 255, 255, 0.15);
}

#sound-toggle:active {
    transform: scale(0.95);
    box-shadow: 0 0 10px rgba(255, 255, 255, 0.2), inset 0 0 8px rgba(255, 255, 255, 0.1);
}

#sound-toggle.sound-off {
    background-color: rgba(100, 100, 100, 0.2);
    border-color: rgba(150, 150, 150, 0.3);
}

#sound-toggle.sound-off:hover {
    background-color: rgba(120, 120, 120, 0.25);
    border-color: rgba(180, 180, 180, 0.4);
}

.sound-icon {
    width: 24px;
    height: 24px;
    color: white;
    display: block;
}

.sound-icon .sound-on-icon {
    display: block;
}

.sound-icon .sound-off-icon {
    display: none;
}

#sound-toggle.sound-off .sound-icon .sound-on-icon {
    display: none;
}

#sound-toggle.sound-off .sound-icon .sound-off-icon {
    display: block;
}