body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    margin: 0;
    padding-bottom: 300px;
}

section {
    min-height: 80vh;
    padding: 50px;
    border-bottom: 2px dashed #ccc;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

/* ===== BÀI 1 ===== */
.container-flex {
    display: flex;
    gap: 20px;
}

.box {
    width: 100px;
    height: 100px;
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 8px;
    font-weight: bold;
}

.box-red { background: #e74c3c; }
.box-green { background: #2ecc71; }
.box-blue { background: #3498db; }
.box-orange { background: #e67e22; }

/* ===== BÀI 3 ===== */
.gsap-box {
    opacity: 0;
    transform: translateX(-100px);
}

/* ===== BÀI 4 ===== */
#bai4 {
    background: #f4f4f4;
}

.header-anim {
    background: #2c3e50;
    color: white;
    padding: 20px;
    width: 100%;
    text-align: center;
}

.hero-cta {
    padding: 12px 30px;
    background: #e74c3c;
    color: white;
    border: none;              /* ✅ SỬA LỖI */
    border-radius: 5px;
    cursor: pointer;
}

/* ===== BÀI 5 (SỬA CHÍNH Ở ĐÂY) ===== */
.card-list {
    display: flex;             /* ✅ Xếp ngang */
    gap: 20px;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;           /* Responsive */
    margin-top: 30px;
}

.card {
    width: 150px;
    height: 200px;
    background: #8e44ad;
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 10px;
    opacity: 0;
    transform: translateY(50px);
}
#bai5 {
    background-image: url("../images/bg.jpg");
    background-size: cover;        /* Phủ kín */
    background-position: center;   /* Canh giữa */
    background-repeat: no-repeat;
    color: white;
}
body {
    background-image: url("../images/bg.jpg");
    background-size: cover;
    background-attachment: fixed; /* Hiệu ứng parallax nhẹ */
}