body {
    margin: 0;
    padding: 0;
    height: 100vh;
    font-family: Arial, sans-serif;

    /* Nền sân cỏ */
    background: linear-gradient(
        180deg,
        #2e7d32 0%,
        #388e3c 50%,
        #1b5e20 100%
    );

    /* Tạo vân sân bóng */
    background-size: 100% 40px;
}

/* Thêm lớp overlay tạo vạch sân */
body::before {
    content: "";
    position: absolute;
    width: 100%;
    height: 100%;
    background-image: 
        linear-gradient(white 2px, transparent 2px),
        linear-gradient(90deg, white 2px, transparent 2px);
    background-size: 200px 200px;
    opacity: 0.15;
    pointer-events: none;
}

.ball {
    position: absolute;
    width: 120px;
    height: 120px;
    bottom: 30px;
    right: 30px;

    background: url('https://upload.wikimedia.org/wikipedia/commons/d/d3/Soccerball.svg') no-repeat center/cover;
    
    border-radius: 50%;
    box-shadow: 0 10px 25px rgba(0,0,0,0.6);

    animation: bounce 1.8s infinite ease-in-out,
               spin 6s linear infinite;
}

@keyframes spin {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
}

/* Hiệu ứng nảy */
@keyframes bounce {
    0%, 100% {
        transform: translateY(0) scale(1);
    }
    40% {
        transform: translateY(-35px) scale(1.05);
    }
    60% {
        transform: translateY(-20px) scale(0.95);
    }
}

.title {
    position: absolute;
    top: 20px;              /* cách mép trên */
    left: 50%;
    transform: translateX(-50%);
    
    font-size: 48px;        /* chữ to */
    font-weight: bold;
    color: #ffffff;

    text-align: center;
    text-shadow: 2px 2px 8px rgba(0, 0, 0, 0.7); /* nổi trên nền */
}

.menu {
    position: absolute;
    top: 120px;
    left: 50%;
    transform: translateX(-50%);
    color: white;
    font-size: 22px;
    text-align: left;
}

/* Tiêu đề mùa */
.season-title {
    font-weight: bold;
    font-size: 26px;
    margin-top: 15px;
}

/* Nhánh nhỏ */
.submenu {
    margin-left: 20px;
    margin-top: 5px;
    opacity: 0.9;
}

/* Link click được */
.link {
    display: block;
    text-decoration: none;
    color: #a5ffb2;
    transition: 0.3s;
}

/* Hover đẹp hơn */
.link:hover {
    color: #00ff88;
    transform: translateX(5px);
    text-shadow: 0 0 8px #00ff88;
}