/* dark mode */
:root {
    --color-primary: #0a192f;
    --color-secondary: #172a45;
    --color-accent: #64ffda;
    --color-text-main: #ccd6f6;
    --color-text-dim: #8892b0;
    --color-bg: #0a192f;
    --color-white: #e6f1ff;
    --shadow: rgba(2, 12, 27, 0.7);
    --nav-bg: rgba(10, 25, 47, 0.95);
}

/* light mode */
@media (prefers-color-scheme: light) {
    :root {
        --color-primary: #F7F7F2;

        --color-secondary: #EBEBE6;

        --color-accent: #004d40;

        /* text color */
        --color-text-main: #2c3e50;
        --color-text-dim: #5d6d7e;

        --color-bg: #F7F7F2;
        --color-white: #1a202c;
        --shadow: rgba(0, 0, 0, 0.05);
        --nav-bg: rgba(247, 247, 242, 0.95);
    }
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    background-color: var(--color-primary);
    color: var(--color-text-main);
    font-family: var(--font-body);
    line-height: 1.6;

    display: flex;
    flex-direction: column;
    min-height: 100vh;
    overflow-x: hidden;
}

main {
    flex: 1;
    display: flex;
    flex-direction: column;
    justify-content: center;
}

a {
    text-decoration: none;
    color: inherit;
    transition: color 0.3s ease;
}

/* --- Navigation --- */
header.site-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 40px;
    height: var(--nav-height);
    background-color: var(--nav-bg);
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
    backdrop-filter: blur(10px);
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.logo {
    font-family: var(--font-heading);
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-accent);
}

/* Logo hover */
a.logo:hover {
    opacity: 0.8;
    cursor: pointer;
}

.nav-links {
    display: flex;
    gap: 30px;
    list-style: none;
}

.nav-links a {
    font-size: 0.9rem;
    color: var(--color-text-main);
    font-weight: 500;
}

.nav-links a:hover, .nav-links a.active {
    color: var(--color-accent);
}

/* --- Button --- */
.btn {
    display: inline-block;
    padding: 12px 24px;
    border: 1px solid var(--color-accent);
    color: var(--color-accent);
    border-radius: 4px;
    font-family: var(--font-body);
    font-size: 14px;
    margin-top: 20px;
    transition: all 0.3s ease;
}

.btn:hover {
    background-color: rgba(100, 255, 218, 0.1);
}

/* --- Footer --- */

footer {
    text-align: center;
    padding: 20px 0;
    background-color: transparent;

    width: 100%;
}

.footer-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 10px;
}

/* --- social meida --- */
.social-links {
    display: flex;
    gap: 20px;
    justify-content: center;
    align-items: center;
}

.social-links a {
    color: var(--color-text-dim);
    transition: transform 0.2s ease, color 0.2s ease;
    display: flex;
}

.social-links a:hover {
    color: var(--color-accent);
    transform: translateY(-3px);
}

.social-links svg {
    width: 20px;
    height: 20px;
}

.copyright {
    font-size: 13px;
    color: var(--color-text-dim);
    opacity: 0.8;
}

.fade-in-up {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

.fade-in-up.visible {
    opacity: 1;
    transform: translateY(0);
}

/* --- Mobile Navigation (Hamburger) --- */
.hamburger {
    display: none;
    cursor: pointer;
}

.bar {
    display: block;
    width: 25px;
    height: 3px;
    margin: 5px auto;
    -webkit-transition: all 0.3s ease-in-out;
    transition: all 0.3s ease-in-out;
    background-color: var(--color-accent);
    border-radius: 2px;
}

/* 移动端样式 (当屏幕宽度小于 768px 时生效) */
@media (max-width: 768px) {
    .hamburger {
        display: block;
        z-index: 2000;

        margin-left: auto;
    }

    .hamburger.active .bar:nth-child(2) {
        opacity: 0;
    }

    .hamburger.active .bar:nth-child(1) {
        transform: translateY(8px) rotate(45deg);
    }

    .hamburger.active .bar:nth-child(3) {
        transform: translateY(-8px) rotate(-45deg);
    }

    .nav-links {
        position: fixed;
        left: -100%;
        top: 0;
        gap: 0;
        flex-direction: column;
        background-color: var(--color-primary);
        width: 100%;
        height: 100vh;
        text-align: center;
        transition: 0.3s;
        padding-top: 120px;
        z-index: 1500;
        box-shadow: 0 10px 20px rgba(0,0,0,0.2);
    }

    .nav-links.active {
        left: 0;
    }

    .nav-links li {
        margin: 25px 0;
    }

    .nav-links a {
        font-size: 1.5rem;
    }
}