:root {
    --nav-progress: 0;

    /* Theme*/
    --bg-color: #111;
    --text-color: #f5f5f5;
    --muted-text: #ddd;
    --hero-gradient: radial-gradient(circle at top left, #444444, #222222 55%, #202020);
    --card-bg: #000;
    --transparent-bg: rgba(0, 0, 0, 0.9);
    --nav-bg-rgb: 5, 5, 5;
    --icon-bg: rgba(0, 0, 0, 0.6);
    --icon-border: rgba(255, 255, 255, 0.4);
    --footer-bg: linear-gradient(to bottom, transparent, #050505);
    --control-bg: #222;
    --control-border: #444;
}

/* Light theme */
body.light-theme {
    --bg-color: #f5f5f5;
    --text-color: #111;
    --muted-text: #333;
    --hero-gradient: radial-gradient(circle at top left, #ffffff, #e0e0e0 55%, #bdbdbd);
    --transparent-bg: rgba(255, 255, 255, 0.9);
    --card-bg: #ffffff;
    --nav-bg-rgb: 255, 255, 255;
    --icon-bg: rgba(255, 255, 255, 0.9);
    --icon-border: rgba(0, 0, 0, 0.25); 
    --footer-bg: linear-gradient(to bottom, transparent, #ffffff);
    --control-bg: #ffffff;
    --control-border: #cccccc;
}


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

body {
    font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    background: var(--bg-color);
    color: var(--text-color);
    overflow-x: hidden;
    transition: background 0.25s ease, color 0.25s ease;
}

/* top Bar */
.site-header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 70px;
    z-index: 100;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(var(--nav-bg-rgb), calc(0.0 + 0.9 * var(--nav-progress)));
    backdrop-filter: blur(calc(6px * var(--nav-progress)));
    transition: background 0.25s ease;
}

.site-header-inner {
    width: 100%;
    max-width: 100vw;
    padding-inline: 1.5rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-logo {
    font-weight: 700;
    letter-spacing: 0.15em;
    text-transform: uppercase;
    font-size: 0.95rem;
    opacity: var(--nav-progress);
    transform: translateY(calc(10px * (1 - var(--nav-progress))));
    transition: opacity 0.2s ease, transform 0.2s ease;
    white-space: nowrap;
    margin-left: 10px;
}

.nav-bar-links {
    display: flex;
    gap: 0.75rem;
    align-items: center;
    opacity: var(--nav-progress);
    transform: translateY(calc(10px * (1 - var(--nav-progress))));
    transition: opacity 0.2s ease, transform 0.2s ease;
}

.nav-link-icon {
    width: 32px;
    height: 32px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
    transition: transform 0.2s ease;
}

.nav-link-icon img {
    width: 100%;
    height: auto;
    transition: transform 0.2s ease;
}

.nav-link-icon img:hover {
    transform: scale(1.1);
    border-color: transparent;
}

/* circle */
.brand-circle {
    position: fixed;
    top: calc(50vh - (50vh - 40px) * var(--nav-progress));
    left: calc(50vw - (50vw - 80px) * var(--nav-progress));
    transform: translate(-50%, -50%) scale(calc(1 - 0.5 * var(--nav-progress)));
    width: 260px;
    height: 260px;
    border-radius: 50%;
    background: var(--transparent-bg);
    color: var(--text-color);
    backdrop-filter: blur(4px);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 0.25rem;
    text-align: center;
    box-shadow: 0 20px 50px rgba(0, 0, 0, 0.5);
    z-index: 90;
    pointer-events: none;
    opacity: calc(1 - var(--nav-progress));
    transition: background 0.25s ease, color 0.25s ease;
}

.brand-main {
    font-size: 2rem;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.brand-subtitle {
    font-size: 0.95rem;
    opacity: 0.8;
}

/* hero */
.hero {
    height: 100vh;
    width: 100vw;
    background: var(--hero-gradient);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 2rem;
    padding-top: 80px;
    transition: background 0.25s ease;
}

.hero-canvas {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    display: block;
    z-index: 0;
}

.hero-content {
    max-width: 600px;
    text-align: center;
}

.hero-content h1 {
    font-size: 2.4rem;
    margin-bottom: 1rem;
}

.hero-content p {
    font-size: 1.1rem;
    color: var(--muted-text);
    line-height: 1.6;
}

/* content */
.content {
    min-height: auto;
    background: var(--bg-color);
    transition: background 0.25s ease;
    margin-left: 5%;
    margin-right: 5%;
    margin-top: 3rem;
}

.content h1 {
    color: var(--muted-text);
    font-size: 2.5rem;
    margin-top: 2rem;
}

.content p {
    line-height: 1.5;
    color: var(--muted-text);
    font-size: 1.4rem;
    margin-top: 2rem;
    margin-left: 1%;
}

.link {
    font-weight: bold; 
    color: var(--text-color);
}

.wave-divider {
    position: relative;
    height: 200px;    
    overflow: visible;
}

.wave-canvas {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 130%;        
    will-change: transform;
    pointer-events: none;
}

/* footer */
.site-footer {
    background: var(--footer-bg);
    padding: 1rem 1.5rem;
    margin-top: 3rem;
}

.footer-inner {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    flex-direction: column;
    gap: 1rem;
    flex-wrap: wrap;
    font-size: 0.9rem;
}

.footer-row {
    display: flex;
    gap: 20px;
}

.footer-section {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.footer-label {
    opacity: 0.8;
}

.footer-select, .theme-toggle-btn {
    appearance: none;
    border-radius: 999px;
    border: 1px solid var(--control-border);
    background: var(--control-bg);
    color: var(--text-color);
    font-size: 1rem;
    cursor: pointer;
    outline: none;
    transition: background 0.2s ease, border-color 0.2s ease, transform 0.1s ease;
}

.footer-select {
    padding: 0.4rem 1rem;
}

.theme-toggle-btn {
    padding: 0.35rem 0.9rem;
}

.footer-select:focus, .theme-toggle-btn:focus {
    border-color: #4f46e5;
    box-shadow: 0 0 0 1px rgba(79, 70, 229, 0.5);
}

.footer-select:hover,
.theme-toggle-btn:hover {
    transform: translateY(-1px);
}

.theme-toggle-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    border-radius: 999px;
    white-space: nowrap;
}

.theme-toggle-icon {
    font-size: 1rem;
}


@media (max-width: 600px) {
    .brand-circle {
        width: 200px;
        height: 200px;
    }

    .brand-main {
        font-size: 1.5rem;
    }

    .site-header-inner {
        padding-inline: 1rem;
    }

    .footer-inner {
        flex-direction: column;
        align-items: center;
    }
}