/* 1. Cài đặt chung */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background: linear-gradient(135deg,#f8fafc,#eef2f7);
    display: grid;
    grid-template-columns: 1fr 300px;
    gap: 24px;
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

/* 2. Header & Nav */
header {
    grid-column: 1 / span 2;
    background: linear-gradient(135deg,#1e3a8a,#2563eb);
    color: white;
    padding: 45px;
    text-align: center;
    border-radius: 18px;
    box-shadow: 0 10px 30px rgba(37,99,235,0.35);
}

nav {
    grid-column: 1 / span 2;
    background: #ffffff;
    border-radius: 14px;
    margin-top: 10px;
    padding: 14px;
    box-shadow: 0 8px 20px rgba(0,0,0,0.08);
}

nav ul {
    list-style: none;
    display: flex;
    justify-content: center;
}

nav ul li { margin: 0 22px; }

nav ul li a {
    color: #1e3a8a;
    text-decoration: none;
    font-weight: 700;
    text-transform: uppercase;
    transition: 0.3s;
}

nav ul li a:hover {
    color: #f97316;
}

/* 3. Danh sách sản phẩm */
.product-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 25px;
}

.product-card {
    background: #ffffff;
    padding: 22px;
    border-radius: 18px;
    text-align: center;
    transition: all 0.4s ease;
    border: none;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    box-shadow: 0 10px 25px rgba(0,0,0,0.08);
}

.product-card:hover {
    transform: translateY(-12px);
    box-shadow: 0 18px 40px rgba(0,0,0,0.18);
}

.product-card img {
    width: 100%;
    border-radius: 14px;
    margin-bottom: 15px;
}

.product-card h2 {
    font-size: 1.25rem;
    color: #0f172a;
    margin-bottom: 10px;
}

.product-card p {
    color: #64748b;
    font-size: 0.95rem;
    margin-bottom: 12px;
}

/* 4. Sidebar */
.sidebar {
    background: linear-gradient(135deg,#0ea5e9,#2563eb);
    border-radius: 18px;
    padding: 30px;
    color: white;
    height: fit-content;
    box-shadow: 0 12px 30px rgba(14,165,233,0.4);
}

.social-icons a {
    display: block;
    color: white;
    text-decoration: none;
    padding: 12px;
    margin-bottom: 12px;
    background: rgba(255,255,255,0.18);
    border-radius: 10px;
    text-align: center;
    transition: 0.3s;
    font-weight: 600;
}

.social-icons a:hover {
    background: white;
    color: #2563eb;
}

/* 5. Nút bấm */
.button {
    padding: 13px 26px;
    border: none;
    cursor: pointer;
    font-weight: bold;
    text-decoration: none;
    display: inline-block;
    transition: 0.3s;
    margin-top: 12px;
}

.button4 {
    background: linear-gradient(90deg,#f97316,#fb923c);
    color: white;
    border-radius: 14px;
}

.button4:hover {
    background: linear-gradient(90deg,#ea580c,#f97316);
    transform: translateY(-3px);
}

/* 6. Footer */
.footer {
    grid-column: 1 / span 2;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
    background: #0f172a;
    color: white;
    padding: 45px;
    border-radius: 18px;
    margin-top: 30px;
}

.footer-item h3 {
    border-bottom: 2px solid #f97316;
    padding-bottom: 10px;
    margin-bottom: 15px;
}

/* 7. Responsive */
@media (max-width: 768px) {
    body { grid-template-columns: 1fr; }
    header, nav, .sidebar, .footer { grid-column: 1; }
    .footer { grid-template-columns: 1fr; }
}