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

:root {
    --font-base: "Open Sans", sans-serif;
    --font-size-base: 1rem;

    --color-text: #ffffff;
    --color-text-shadow: rgba(0, 0, 0, 0.5);
    --primary-color: #FFDE9F;
    --color-auth-bg: var(--primary-color);
    --color-auth-text: #1a1a1a;
    --color-focus-ring: var(--primary-color);
    --color-overlay: rgba(0, 0, 0, 0.55);
    --color-mobile-menu-bg: rgba(15, 15, 15, 0.97);

    --header-padding-x: clamp(1rem, 4vw, 2.5rem);
    --header-padding-y: 1rem;
    --nav-gap: 1.75rem;
    --auth-padding: 0.5rem 1.125rem;
    --border-radius-btn: 6px;
    --border-radius-focus: 6px;

    --transition-overlay: opacity 250ms ease, visibility 250ms ease;
    --transition-menu: opacity 200ms ease, transform 200ms ease;
}

body {
    font-family: var(--font-base), serif;
    font-size: var(--font-size-base);
    background: #2a3d55 url("https://images.unsplash.com/photo-1506744038136-46273834b3fb?w=1600&q=80") center/cover no-repeat;
    min-height: 100vh;
}

.nav-overlay {
    position: fixed;
    inset: 0;
    background: var(--color-overlay);
    opacity: 0;
    visibility: hidden;
    transition: var(--transition-overlay);
    z-index: 90;

    &.is-active {
        opacity: 1;
        visibility: visible;
    }
}

.site-header {
    position: relative;
    top: 0;
    z-index: 100;
    width: 100%;
    display: flex;
    flex-direction: column;
    background: rgba(15, 15, 15, 0.55);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--header-padding-y) var(--header-padding-x);
    gap: 1rem;
}

.site-title {
    font-size: var(--font-size-base);
    font-weight: 700;
    color: var(--color-text);
    text-decoration: none;
    white-space: nowrap;
    flex-shrink: 0;
    text-shadow:
            0 0px 8px var(--color-text-shadow),
            0 0px 30px var(--color-text-shadow);

    &:focus-visible {
        outline: 3px solid var(--color-focus-ring);
        outline-offset: 4px;
        border-radius: var(--border-radius-focus);
    }
}

.primary-nav {
    & ul {
        display: flex;
        align-items: center;
        gap: var(--nav-gap);
        list-style: none;
    }

    & a:not(.btn-auth) {
        font-size: var(--font-size-base);
        font-weight: 600;
        color: var(--color-text);
        text-decoration: none;
        white-space: nowrap;
        text-shadow:
                0 0px 8px var(--color-text-shadow),
                0 0px 30px var(--color-text-shadow);

        padding: 0.2rem 0;
        border-bottom: 1px solid transparent;
        transition: color 200ms ease, border-color 200ms ease;

        &:hover {
            color: #ffffff;
            border-bottom-color: rgba(255, 255, 255, 0.6);
        }

        &:focus-visible {
            outline: 3px solid var(--color-focus-ring);
            outline-offset: 4px;
            border-radius: var(--border-radius-focus);
        }
    }
}

.btn-auth {
    display: inline-flex;
    align-items: center;
    background-color: var(--color-auth-bg);
    color: var(--color-auth-text);
    font-weight: 700;
    padding: var(--auth-padding);
    border-radius: var(--border-radius-btn);
    text-decoration: none;
    white-space: nowrap;
    text-shadow: none;
    box-shadow:0 1px 10px rgba(0,0,0,0.3);
    transition: filter var(--transition), transform var(--transition), box-shadow var(--transition);

    &:hover {
        filter: brightness(0.8);
        box-shadow: 0 4px 14px rgba(255, 222, 159, 0.25);
        transform: translateY(-1px);
        text-decoration: none;
    }

    &:focus-visible {
        outline: 3px solid var(--color-focus-ring);
        outline-offset: 3px;
        border-radius: var(--border-radius-focus);
        text-decoration: none;
    }

    .icon-auth {
        margin-right:  0.5rem;
    }
}

.menu-toggle {
    display: none;
    align-items: center;
    gap: 0.4rem;
    background: transparent;
    border: none;
    cursor: pointer;
    color: var(--color-text);
    font-family: var(--font-base);
    font-size: var(--font-size-base);
    font-weight: 600;
    padding: 0.25rem;
    border-radius: 4px;
    flex-shrink: 0;
    filter: drop-shadow(0 1px 4px rgba(0,0,0,0.45));
    text-shadow:
            0 0px 8px var(--color-text-shadow),
            0 0px 30px var(--color-text-shadow);

    &:focus-visible {
        outline: 3px solid var(--color-focus-ring);
        outline-offset: 4px;
        border-radius: var(--border-radius-focus);
    }
}

.mobile-nav {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    z-index: 95;
    background: var(--color-mobile-menu-bg);
    padding: 1rem var(--header-padding-x) 1.5rem;
    opacity: 0;
    pointer-events: none;
    transform: translateY(-6px);
    transition: var(--transition-menu);

    &.is-open {
        opacity: 1;
        pointer-events: auto;
        transform: translateY(0);
    }

    & ul {
        list-style: none;
        display: flex;
        flex-direction: column;
    }

    & li {
        border-bottom: 1px solid rgba(255,255,255,0.08);

        &:last-child {
            border-bottom: none;
            padding-top: 1rem;
        }
    }

    & a:not(.btn-auth) {
        display: block;
        padding: 1rem 0.5rem;
        margin: 0 -0.5rem;
        font-size: var(--font-size-base);
        font-weight: 600;
        color: var(--color-text);
        text-decoration: none;
        text-shadow: none;
        border-bottom-style: solid;
        border-bottom-width: 1px;
        border-bottom-color: transparent;
        transition: color 200ms ease, border-color 200ms ease;

        &:hover {
            color: #ffffff;
            border-bottom-color: rgba(255, 255, 255, 0.6);
        }

        &:focus-visible {
            outline: 3px solid var(--color-focus-ring);
            outline-offset: 2px;
            border-radius: var(--border-radius-focus);
        }
    }

    & .btn-auth {
        padding: 0.5rem 1rem;
    }
}

@media (max-width: 768px) {
    .primary-nav { display: none; }
    .menu-toggle  { display: flex; }
}

@media (prefers-reduced-motion: reduce) {
    .nav-overlay,
    .mobile-nav {
        transition: none;
    }
}