body {
    margin: 0;
    font-family: 'Poppins', sans-serif;
    color: #eee;
    background: #111; /* 纯色底 */
}
.logo img {
    height: 28px;
}
.hero {
    min-height: 100vh;          /* 满整屏 */
    display: flex;
    align-items: center;        /* 垂直居中 */
    justify-content: center;    /* 水平居中 */
    text-align: center;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: "";
    position: absolute;
    inset: 0;
    background:
        linear-gradient(to bottom, rgba(0,0,0,0.4), rgba(0,0,0,0.8)),
        url("../images/background.jpg") center/cover no-repeat;
    z-index: 0;
}

.hero .container {
    position: relative;
    z-index: 1;
}


.container {
    width: 90%;
    max-width: 1100px;
    margin: auto;
}

.navbar {
    background: #1b1b1b;
    padding: 15px 0;
}

.nav-flex {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 22px;
    font-weight: bold;
}

nav a {
    color: #ccc;
    margin-left: 20px;
    text-decoration: none;
}

nav a:hover {
    color: #4caf50;
}

.btn-primary {
    background: #4caf50;
    padding: 12px 25px;
    border-radius: 30px;
    color: white;
    text-decoration: none;
}

.services-preview h2 {
    text-align: center;
    margin: 60px 0 30px;
}

.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 20px;
}

.card {
    background: #1e1e1e;
    padding: 25px;
    border-radius: 20px;
    box-shadow: 0 5px 15px rgba(0,0,0,0.4);
}

.why-us {
    padding: 70px 0;
}

footer {
    text-align: center;
    padding: 30px 0;
    background: #1b1b1b;
    margin-top: 50px;
}
.fade-in {
    opacity: 0;
    transform: translateY(20px);
    animation: fadeUp 0.8s ease forwards;
}

@keyframes fadeUp {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}