.bkbg-fc-app {
    font-family: system-ui, -apple-system, sans-serif;
    box-sizing: border-box;
}

.bkbg-fc-wrap {
    border-radius: 12px;
    padding: 28px;
    margin: 0 auto;
}

.bkbg-fc-title {
    font-family: var(--bkbg-flash-tt-font-family, inherit);
    font-size: var(--bkbg-flash-tt-font-size-d, 26px);
    font-weight: var(--bkbg-flash-tt-font-weight, 700);
    line-height: var(--bkbg-flash-tt-line-height-d, 1.2);
    text-transform: var(--bkbg-flash-tt-text-transform, none);
    font-style: var(--bkbg-flash-tt-font-style, normal);
    text-decoration: var(--bkbg-flash-tt-text-decoration, none);
    letter-spacing: var(--bkbg-flash-tt-letter-spacing-d, normal);
    word-spacing: var(--bkbg-flash-tt-word-spacing-d, normal);
    margin: 0 0 6px;
}

.bkbg-fc-subtitle {
    font-family: var(--bkbg-flash-ts-font-family, inherit);
    font-size: var(--bkbg-flash-ts-font-size-d, 15px);
    font-weight: var(--bkbg-flash-ts-font-weight, 400);
    line-height: var(--bkbg-flash-ts-line-height-d, 1.5);
    text-transform: var(--bkbg-flash-ts-text-transform, none);
    font-style: var(--bkbg-flash-ts-font-style, normal);
    text-decoration: var(--bkbg-flash-ts-text-decoration, none);
    letter-spacing: var(--bkbg-flash-ts-letter-spacing-d, normal);
    word-spacing: var(--bkbg-flash-ts-word-spacing-d, normal);
    margin: 0 0 20px;
}

/* Progress */
.bkbg-fc-progress-row {
    display: flex;
    justify-content: space-between;
    font-size: 13px;
    margin-bottom: 6px;
}

.bkbg-fc-progress-bar-wrap {
    height: 8px;
    background: #e5e7eb;
    border-radius: 4px;
    margin-bottom: 20px;
    overflow: hidden;
}

.bkbg-fc-progress-bar {
    height: 100%;
    border-radius: 4px;
    transition: width 0.4s ease;
}

/* Card flip */
.bkbg-fc-scene {
    perspective: 1000px;
    margin-bottom: 20px;
}

.bkbg-fc-card {
    position: relative;
    width: 100%;
    transition: transform 0.5s;
    transform-style: preserve-3d;
    cursor: pointer;
}

.bkbg-fc-card.bkbg-fc-flipped {
    transform: rotateY(180deg);
}

.bkbg-fc-face {
    position: absolute;
    inset: 0;
    border-radius: 14px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    text-align: center;
    padding: 24px 32px;
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
    box-shadow: 0 8px 32px rgba(0,0,0,0.12);
}

.bkbg-fc-front {
    font-family: var(--bkbg-flash-tc-font-family, inherit);
    font-size: var(--bkbg-flash-tc-font-size-d, 18px);
    font-weight: var(--bkbg-flash-tc-font-weight, 500);
    line-height: var(--bkbg-flash-tc-line-height-d, 1.5);
    text-transform: var(--bkbg-flash-tc-text-transform, none);
    font-style: var(--bkbg-flash-tc-font-style, normal);
    text-decoration: var(--bkbg-flash-tc-text-decoration, none);
    letter-spacing: var(--bkbg-flash-tc-letter-spacing-d, normal);
    word-spacing: var(--bkbg-flash-tc-word-spacing-d, normal);
}

.bkbg-fc-back {
    transform: rotateY(180deg);
    font-family: var(--bkbg-flash-tc-font-family, inherit);
    font-size: var(--bkbg-flash-tc-font-size-d, 22px);
    font-weight: var(--bkbg-flash-tc-font-weight, 700);
    line-height: var(--bkbg-flash-tc-line-height-d, 1.5);
    text-transform: var(--bkbg-flash-tc-text-transform, none);
    font-style: var(--bkbg-flash-tc-font-style, normal);
    text-decoration: var(--bkbg-flash-tc-text-decoration, none);
    letter-spacing: var(--bkbg-flash-tc-letter-spacing-d, normal);
    word-spacing: var(--bkbg-flash-tc-word-spacing-d, normal);
}

.bkbg-fc-flip-hint {
    font-size: 12px;
    opacity: 0.5;
    margin-top: 12px;
    position: absolute;
    bottom: 14px;
    right: 18px;
}

.bkbg-fc-known-badge {
    position: absolute;
    top: 12px;
    left: 12px;
    border-radius: 20px;
    padding: 3px 10px;
    font-size: 11px;
    font-weight: 700;
    display: flex;
    align-items: center;
    gap: 4px;
}

/* Navigation */
.bkbg-fc-nav {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 10px;
    margin-bottom: 12px;
    flex-wrap: wrap;
}

.bkbg-fc-nav-btn {
    border: none;
    border-radius: 8px;
    padding: 10px 18px;
    font-size: 20px;
    cursor: pointer;
    transition: filter 0.15s, transform 0.1s;
    background: #e5e7eb;
    color: #374151;
}

.bkbg-fc-nav-btn:hover { filter: brightness(0.9); transform: scale(1.05); }
.bkbg-fc-nav-btn:disabled { opacity: 0.4; cursor: default; transform: none; }

.bkbg-fc-known-btn {
    border: none;
    border-radius: 8px;
    padding: 10px 18px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: filter 0.15s;
    color: #fff;
}

.bkbg-fc-known-btn:hover { filter: brightness(0.9); }

.bkbg-fc-counter-row {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 10px;
    flex-wrap: wrap;
    font-size: 13px;
}

.bkbg-fc-counter {
    opacity: 0.7;
}

.bkbg-fc-action-btn {
    background: transparent;
    border-radius: 6px;
    padding: 4px 12px;
    font-size: 12px;
    cursor: pointer;
    transition: background 0.15s;
}

.bkbg-fc-action-btn:hover { opacity: 0.8; }

.bkbg-fc-keyboard-hint {
    text-align: center;
    font-size: 12px;
    margin-top: 12px;
    opacity: 0.55;
}

/* Summary screen */
.bkbg-fc-summary {
    text-align: center;
    padding: 40px 20px;
}

.bkbg-fc-summary-icon {
    font-size: 56px;
    margin-bottom: 16px;
}

.bkbg-fc-summary h3 {
    margin: 0 0 8px;
    font-size: 22px;
}

.bkbg-fc-summary p {
    font-size: 15px;
    margin-bottom: 20px;
    opacity: 0.7;
}

.bkbg-fc-restart-btn {
    border: none;
    border-radius: 8px;
    padding: 12px 28px;
    font-size: 15px;
    font-weight: 600;
    cursor: pointer;
    color: #fff;
    transition: filter 0.15s;
}

.bkbg-fc-restart-btn:hover { filter: brightness(0.9); }

/* Typography responsive */
@media (max-width: 1024px) {
    .bkbg-fc-title {
        font-size: var(--bkbg-flash-tt-font-size-t, var(--bkbg-flash-tt-font-size-d, 26px));
        line-height: var(--bkbg-flash-tt-line-height-t, var(--bkbg-flash-tt-line-height-d, 1.2));
        letter-spacing: var(--bkbg-flash-tt-letter-spacing-t, var(--bkbg-flash-tt-letter-spacing-d, normal));
        word-spacing: var(--bkbg-flash-tt-word-spacing-t, var(--bkbg-flash-tt-word-spacing-d, normal));
    }
    .bkbg-fc-subtitle {
        font-size: var(--bkbg-flash-ts-font-size-t, var(--bkbg-flash-ts-font-size-d, 15px));
        line-height: var(--bkbg-flash-ts-line-height-t, var(--bkbg-flash-ts-line-height-d, 1.5));
        letter-spacing: var(--bkbg-flash-ts-letter-spacing-t, var(--bkbg-flash-ts-letter-spacing-d, normal));
        word-spacing: var(--bkbg-flash-ts-word-spacing-t, var(--bkbg-flash-ts-word-spacing-d, normal));
    }
    .bkbg-fc-front {
        font-size: var(--bkbg-flash-tc-font-size-t, var(--bkbg-flash-tc-font-size-d, 18px));
        line-height: var(--bkbg-flash-tc-line-height-t, var(--bkbg-flash-tc-line-height-d, 1.5));
        letter-spacing: var(--bkbg-flash-tc-letter-spacing-t, var(--bkbg-flash-tc-letter-spacing-d, normal));
        word-spacing: var(--bkbg-flash-tc-word-spacing-t, var(--bkbg-flash-tc-word-spacing-d, normal));
    }
    .bkbg-fc-back {
        font-size: var(--bkbg-flash-tc-font-size-t, var(--bkbg-flash-tc-font-size-d, 22px));
        line-height: var(--bkbg-flash-tc-line-height-t, var(--bkbg-flash-tc-line-height-d, 1.5));
        letter-spacing: var(--bkbg-flash-tc-letter-spacing-t, var(--bkbg-flash-tc-letter-spacing-d, normal));
        word-spacing: var(--bkbg-flash-tc-word-spacing-t, var(--bkbg-flash-tc-word-spacing-d, normal));
    }
}

@media (max-width: 767px) {
    .bkbg-fc-title {
        font-size: var(--bkbg-flash-tt-font-size-m, var(--bkbg-flash-tt-font-size-t, var(--bkbg-flash-tt-font-size-d, 26px)));
        line-height: var(--bkbg-flash-tt-line-height-m, var(--bkbg-flash-tt-line-height-t, var(--bkbg-flash-tt-line-height-d, 1.2)));
        letter-spacing: var(--bkbg-flash-tt-letter-spacing-m, var(--bkbg-flash-tt-letter-spacing-t, var(--bkbg-flash-tt-letter-spacing-d, normal)));
        word-spacing: var(--bkbg-flash-tt-word-spacing-m, var(--bkbg-flash-tt-word-spacing-t, var(--bkbg-flash-tt-word-spacing-d, normal)));
    }
    .bkbg-fc-subtitle {
        font-size: var(--bkbg-flash-ts-font-size-m, var(--bkbg-flash-ts-font-size-t, var(--bkbg-flash-ts-font-size-d, 15px)));
        line-height: var(--bkbg-flash-ts-line-height-m, var(--bkbg-flash-ts-line-height-t, var(--bkbg-flash-ts-line-height-d, 1.5)));
        letter-spacing: var(--bkbg-flash-ts-letter-spacing-m, var(--bkbg-flash-ts-letter-spacing-t, var(--bkbg-flash-ts-letter-spacing-d, normal)));
        word-spacing: var(--bkbg-flash-ts-word-spacing-m, var(--bkbg-flash-ts-word-spacing-t, var(--bkbg-flash-ts-word-spacing-d, normal)));
    }
    .bkbg-fc-front {
        font-size: var(--bkbg-flash-tc-font-size-m, var(--bkbg-flash-tc-font-size-t, var(--bkbg-flash-tc-font-size-d, 16px)));
        line-height: var(--bkbg-flash-tc-line-height-m, var(--bkbg-flash-tc-line-height-t, var(--bkbg-flash-tc-line-height-d, 1.5)));
        letter-spacing: var(--bkbg-flash-tc-letter-spacing-m, var(--bkbg-flash-tc-letter-spacing-t, var(--bkbg-flash-tc-letter-spacing-d, normal)));
        word-spacing: var(--bkbg-flash-tc-word-spacing-m, var(--bkbg-flash-tc-word-spacing-t, var(--bkbg-flash-tc-word-spacing-d, normal)));
    }
    .bkbg-fc-back {
        font-size: var(--bkbg-flash-tc-font-size-m, var(--bkbg-flash-tc-font-size-t, var(--bkbg-flash-tc-font-size-d, 18px)));
        line-height: var(--bkbg-flash-tc-line-height-m, var(--bkbg-flash-tc-line-height-t, var(--bkbg-flash-tc-line-height-d, 1.5)));
        letter-spacing: var(--bkbg-flash-tc-letter-spacing-m, var(--bkbg-flash-tc-letter-spacing-t, var(--bkbg-flash-tc-letter-spacing-d, normal)));
        word-spacing: var(--bkbg-flash-tc-word-spacing-m, var(--bkbg-flash-tc-word-spacing-t, var(--bkbg-flash-tc-word-spacing-d, normal)));
    }
}

@media (max-width: 480px) {
    .bkbg-fc-wrap { padding: 16px; }
    .bkbg-fc-face { padding: 18px 16px; }
}