:root {
    --background-dark: #0f172a;
    --spacing-s: 8px;
    --spacing-m: 16px;
    --spacing-l: 24px;
    --spacing-xl: 32px;
    --spacing-xxl: 64px;
    --text-light: rgba(255,255,255,0.75);
    --text-lighter: rgba(255,255,255,0.9);
    --width-container: 1200px;

    /* Purple + Orange palette */
    --color-purple: #a855f7;
    --color-orange: #f97316;
    --gradient-primary: linear-gradient(90deg, #a855f7, #f97316);
    --gradient-shimmer: linear-gradient(90deg, #a855f7, #f97316, #a855f7);
    --badge-bg: linear-gradient(135deg, rgba(168,85,247,0.3), rgba(249,115,22,0.3));
    --badge-border: rgba(168, 85, 247, 0.5);
}

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

html {
    height: 100%;
    font-family: 'Montserrat', sans-serif;
    font-size: 16px;
}

body {
    height: 100%;
}

.hero-section {
    align-items: center;
    background: var(--background-dark);
    display: flex;
    min-height: 100%;
    justify-content: center;
    padding: var(--spacing-xxl) var(--spacing-l);
    flex-direction: column;
}

/* Title — shimmer animation */
.assignment-title {
    font-size: 3.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-xxl);
    text-align: center;
    letter-spacing: 2px;
    background: var(--gradient-shimmer);
    background-size: 200% auto;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: shimmer 3s linear infinite;
}

@keyframes shimmer {
    0%   { background-position: 0% center; }
    100% { background-position: 200% center; }
}

.card-grid {
    display: grid;
    grid-template-columns: repeat(1, 1fr);
    grid-column-gap: var(--spacing-l);
    grid-row-gap: var(--spacing-l);
    max-width: var(--width-container);
    width: 100%;
}

@media(min-width: 540px) {
    .card-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media(min-width: 960px) {
    .card-grid {
        grid-template-columns: repeat(4, 1fr);
    }
}

.card {
    list-style: none;
    position: relative;
    text-decoration: none;
}

.card:before {
    content: '';
    display: block;
    padding-bottom: 150%;
    width: 100%;
}

.card__background {
    background-size: cover;
    background-position: center;
    border-radius: var(--spacing-l);
    bottom: 0;
    filter: brightness(0.75) saturate(1.2) contrast(0.85);
    left: 0;
    position: absolute;
    right: 0;
    top: 0;
    transform-origin: center;
    transform: scale(1) translateZ(0);
    transition: filter 200ms linear, transform 200ms linear;
}

.card:hover .card__background {
    transform: scale(1.05) translateZ(0);
}

.card-grid:hover > .card:not(:hover) .card__background {
    filter: brightness(0.5) saturate(0.5) contrast(1.2) blur(20px);
}

.card__content {
    left: 0;
    padding: var(--spacing-l);
    position: absolute;
    top: 0;
}

/* Category — orange to purple gradient */
.card__category {
    font-size: 0.85rem;
    font-weight: 700;
    margin-bottom: var(--spacing-m);
    text-transform: uppercase;
    letter-spacing: 1.5px;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.card__heading {
    color: var(--text-lighter);
    font-size: 1.8rem;
    text-shadow: 2px 2px 20px rgba(0,0,0,0.2);
    line-height: 1.2;
}

/* Badge — optional, add to your HTML */
.card__badge {
    position: absolute;
    bottom: var(--spacing-l);
    right: var(--spacing-l);
    background: var(--badge-bg);
    backdrop-filter: blur(6px);
    color: var(--text-lighter);
    font-size: 0.7rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    padding: 6px 12px;
    border-radius: 100px;
    border: 1px solid var(--badge-border);
}