.past-papers-container {
    padding: 24px;
    height: 100%;
    overflow-y: auto;
    background-color: var(--tool-bg, var(--main-bg));
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.past-papers-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: 18px;
}

.past-paper-card {
    background-color: var(--tool-bg, #fff);
    border: 1px solid var(--border-color, rgba(99, 102, 241, 0.15));
    border-radius: 14px;
    padding: 18px;
    display: flex;
    flex-direction: column;
    gap: 12px;
    box-shadow: 0 8px 24px rgba(15, 23, 42, 0.12);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    cursor: pointer;
}

.past-paper-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 14px 32px rgba(15, 23, 42, 0.18);
}

.past-paper-label {
    font-size: 16px;
    font-weight: 600;
    color: var(--text-primary);
}

.past-paper-year {
    font-size: 13px;
    color: var(--text-secondary);
}

.past-paper-thumbnail {
    width: 100%;
    aspect-ratio: 4 / 3;
    border-radius: 10px;
    overflow: hidden;
    border: 1px solid var(--border-color, rgba(15, 23, 42, 0.08));
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.08), rgba(139, 92, 246, 0.08));
    background: linear-gradient(135deg,
            color-mix(in srgb, var(--accent, #6366f1) 18%, transparent),
            color-mix(in srgb, var(--accent-hover, #8b5cf6) 18%, transparent));
    position: relative;
}

.past-paper-thumbnail iframe {
    width: 100%;
    height: 100%;
    border: none;
    pointer-events: none;
    filter: grayscale(0.1) contrast(0.9);
    background: #fff;
}

.past-paper-thumbnail-placeholder {
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 13px;
    color: var(--text-secondary);
    background: repeating-linear-gradient(45deg,
            color-mix(in srgb, var(--accent, #6366f1) 14%, transparent),
            color-mix(in srgb, var(--accent, #6366f1) 14%, transparent) 10px,
            color-mix(in srgb, var(--accent-hover, #8b5cf6) 14%, transparent) 10px,
            color-mix(in srgb, var(--accent-hover, #8b5cf6) 14%, transparent) 20px);
}

.past-paper-pill-row {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.past-paper-pill {
    padding: 4px 10px;
    border-radius: 999px;
    font-size: 12px;
    font-weight: 500;
    color: #fff;
}

.past-paper-pill.type {
    background: var(--accent);
}

.past-paper-pill.source {
    background: var(--nav-active-bg, rgba(15, 23, 42, 0.65));
    color: var(--text-primary);
}

.past-paper-actions {
    display: flex;
    justify-content: flex-end;
}

.past-paper-open-btn {
    background: var(--accent);
    border: none;
    color: #fff;
    padding: 8px 14px;
    border-radius: 10px;
    font-size: 13px;
    font-weight: 600;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.past-paper-open-btn svg {
    width: 16px;
    height: 16px;
}

.past-paper-open-btn:hover {
    transform: translateY(-1px);
}

.past-papers-empty {
    padding: 80px 20px;
    text-align: center;
    border-radius: 16px;
}

.past-papers-empty h3 {
    font-size: 18px;
    color: var(--text-primary);
    margin-bottom: 8px;
}

.past-papers-empty p {
    color: var(--text-secondary);
    font-size: 14px;
    margin: 0;
}

.past-paper-viewer {
    flex: 1;
    border: none;
    border-radius: 14px;
    margin-top: 12px;
    min-height: 480px;
    width: 100%;
    box-shadow: 0 24px 45px rgba(15, 23, 42, 0.12);
    background: #fff;
}

@media (max-width: 768px) {
    .past-papers-container {
        padding: 16px;
    }

    .past-papers-grid {
        grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    }

    .past-paper-viewer {
        min-height: 360px;
    }
}