/* 歌曲卡片 */
.song-card {
    background: linear-gradient(145deg, #3a5d5f 0%, #2d4a4d 100%);
    border-radius: 1rem;
    overflow: hidden;
    position: relative;
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.25);
    transition: transform 0.4s ease, box-shadow 0.4s ease;
}
.song-card:hover {
    transform: translateY(-6px) scale(1.02);
    box-shadow: 0 12px 30px rgba(0, 0, 0, 0.35);
}

/* 封面圖過渡效果 */
.song-card img {
    transition: transform 0.6s ease, opacity 0.4s ease;
}
.song-card:hover img {
    transform: scale(1.05);
    opacity: 1;
}

/* 版本選擇按鈕 */
.version-badge {
    font-family: "Source Sans Pro", sans-serif;
    font-weight: 600;
    transition: transform 0.25s ease, background-color 0.25s ease, box-shadow 0.25s ease;
}
.version-badge:hover {
    transform: scale(1.08);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.25);
}

/* 不可用遮罩 */
.unavailable-overlay {
    background: linear-gradient(
        45deg,
        rgba(0, 0, 0, 0.7) 30%,
        rgba(54, 84, 86, 0.8) 100%
    );
    backdrop-filter: blur(2px);
    z-index: 10;
    font-size: 1.5rem;
    letter-spacing: 2px;
    color: #fff;
    animation: fadeIn 0.5s ease forwards;
}

.unavailable-overlay:hover {
    backdrop-filter: blur(0.5px);
}

/* 彈性淡入動畫 */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes modalPop {
    0% { transform: translate(-50%, -50%) scale(0.95); opacity: 0; }
    100% { transform: translate(-50%, -50%) scale(1); opacity: 1; }
}

/* 播放按鈕互動效果 */
.song-card button {
    transition: transform 0.25s ease, background-color 0.25s ease;
}
.song-card button:hover {
    transform: scale(1.15);
}

/* 全域動畫微調 */
.song-card,
.version-badge,
.song-card button {
    will-change: transform, box-shadow, opacity;
}