:root {
    --bg-gradient: linear-gradient(135deg, #612121, #5c2a2a);
    --primary-text: #e8e8e8;
    --accent: #ff6f61;
    --card-bg: #2d2d3d;
    --card-hover: #3a3a4d;

    /* New: base wave color in HSL so we can tweak lightness/saturation */
    --wave-base: 0, 75.4%, 43%; /* reddish by default (hue 0°) */
}

body {
    margin: 0;
    font-family: 'Montserrat', sans-serif;
    background: var(--bg-gradient);
    color: var(--primary-text);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 2rem 1rem;
    line-height: 1.6;
    position: relative;
    overflow-x: hidden;
}

.title, h2, p, .cards, footer {
    position: relative;
    z-index: 2;
}

.title {
    font-size: 3.5rem;
    text-align: center;
    margin: 0.5rem 0 1rem;
    color: var(--accent);
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}

h2 {
    font-size: 2rem;
    text-align: center;
    margin: 3.5rem 0 0rem;
    color: var(--accent);
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}

p {
    max-width: 600px;
    margin: 0 auto 1rem;
    font-size: 1.1rem;
    text-align: center;
    color: var(--primary-text);
}

.cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 1.5rem;
    width: 100%;
    max-width: 900px;
    margin-top: 2rem;
}

.card {
    background: var(--card-bg);
    padding: 1.5rem;
    border-radius: 8px;
    text-align: center;
    transition: transform 0.2s ease, background 0.2s ease;
    box-shadow: 0 4px 6px rgba(0,0,0,0.2);
}

.card:hover {
    background: var(--card-hover);
    transform: translateY(-5px);
}

.lang-name {
    font-size: 1.4rem;
    font-weight: 700;
    color: var(--accent);
    margin-bottom: 0.5rem;
}

.lang-level {
    font-size: 1rem;
    color: var(--primary-text);
}

footer {
    margin-top: 3rem;
    font-size: 0.9rem;
    color: #a0a0a0;
    text-align: center;
}

a {
    color: var(--accent);
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

/* ========================= */
/* Animated Sine-like Waves  */
/* ========================= */
.wave-background {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    z-index: 0;
    pointer-events: none;
}

.wave-layer {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;

    /* Ripple waves starting from top-left */
    background: repeating-radial-gradient(
        circle at 0 0, /* << origin in left-upper corner */
        hsla(var(--wave-base), 0.1) 0px,
        hsla(var(--wave-base), 0.1) 5px,
        transparent 20px,
        transparent 40px
    );

    background-size: 150% 150%;
    animation: diagonalShift 25s linear infinite;
    opacity: 0.25;

    /* Performance optimizations */
    will-change: background-position;
    contain: paint;
}

/* Variations across layers */
.wave-layer:nth-child(odd) {
    animation-duration: 24.2s;
    opacity: 0.2;
}
.wave-layer:nth-child(3n) {
    animation-duration: 13.5s;
    opacity: 0.15;
}
.wave-layer:nth-child(5n) {
    filter: brightness(1.1);
}

/* Animate background movement */
@keyframes diagonalShift {
    from { background-position: 0 0; }
    to   { background-position: -300px -300px; }
}