:root {
    --bg: #f3f6fb;
    --panel: #ffffff;
    --panel-alt: #eef4ff;
    --primary: #2d5bff;
    --primary-dark: #2148c6;
    --accent: #eaf3ff;
    --border: #d8e2f1;
    --text: #1d2736;
    --muted: #58657a;
    --success: #0f9d58;
    --warning: #d97706;
    --danger: #cf3b4d;
    --shadow: 0 16px 38px rgba(25, 41, 64, 0.08);
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: "Segoe UI", Arial, Helvetica, sans-serif;
    background: linear-gradient(180deg, #f7f9fc 0%, #eef4ff 100%);
    color: var(--text);
    line-height: 1.45;
}

button,
input {
    font: inherit;
}

button:focus-visible,
input:focus-visible,
.file-picker:focus-within {
    outline: 3px solid rgba(45, 91, 255, 0.28);
    outline-offset: 2px;
}

.app-shell {
    max-width: 1200px;
    margin: 0 auto;
    padding: 32px 20px 48px;
}

.topbar {
    margin-bottom: 24px;
}

.eyebrow {
    margin: 0 0 8px;
    text-transform: uppercase;
    letter-spacing: 0.12em;
    font-size: 12px;
    font-weight: 700;
    color: var(--primary);
}

h1,
h2,
h3,
h4,
p {
    margin-top: 0;
}

h1 {
    margin-bottom: 0;
    font-size: clamp(2rem, 3vw, 2.8rem);
}

.content {
    display: grid;
    gap: 20px;
}

.panel {
    background: var(--panel);
    border: 1px solid var(--border);
    border-radius: 18px;
    box-shadow: var(--shadow);
    padding: 20px;
}

.controls-panel {
    display: grid;
    gap: 16px;
}

.control-row {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    align-items: center;
}

.file-picker {
    position: relative;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 44px;
    border: 1px dashed var(--primary);
    background: var(--accent);
    color: var(--primary);
    border-radius: 12px;
    cursor: pointer;
    transition: transform 0.15s ease, background 0.15s ease;
    overflow: hidden;
}

.file-picker:hover {
    background: #e0ebff;
    transform: translateY(-1px);
}

.file-picker input {
    position: absolute;
    inset: 0;
    opacity: 0;
    cursor: pointer;
}

.file-picker span {
    display: inline-block;
    padding: 0 18px;
    font-weight: 600;
}

.primary-button,
.secondary-button {
    border: 0;
    border-radius: 12px;
    padding: 0 18px;
    min-height: 44px;
    font-weight: 700;
    cursor: pointer;
    transition: transform 0.15s ease, opacity 0.15s ease;
}

.primary-button {
    background: var(--primary);
    color: #fff;
}

.primary-button:hover,
.secondary-button:hover {
    transform: translateY(-1px);
}

.primary-button:disabled,
.secondary-button:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

.secondary-button {
    background: #edf2ff;
    color: var(--primary-dark);
}

.hidden {
    display: none;
}

.batch-size-wrap {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    flex-wrap: wrap;
    padding: 10px 12px;
    border: 1px solid var(--border);
    border-radius: 12px;
    background: #f8fbff;
}

.batch-size-wrap label {
    font-weight: 700;
    color: var(--text);
}

.batch-size-wrap input {
    width: 90px;
    min-height: 38px;
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 0 10px;
    font-weight: 700;
    color: var(--text);
    background: #fff;
}

.status-message {
    min-height: 24px;
    font-weight: 600;
    color: var(--muted);
}

.status-message.error {
    color: var(--danger);
}

.status-message.success {
    color: var(--success);
}

.panel-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    margin-bottom: 16px;
}

.summary-pill {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
    font-weight: 700;
    padding: 6px 12px;
    border-radius: 999px;
    background: #edf3ff;
    color: var(--primary-dark);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 10px;
    margin: -2px 0 20px;
}

.stat-item {
    display: grid;
    gap: 4px;
    min-width: 0;
    padding: 14px;
    border: 1px solid var(--border);
    border-radius: 12px;
    background: #f8fbff;
}

.stat-label {
    overflow: hidden;
    color: var(--muted);
    font-size: 12px;
    font-weight: 700;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.stat-value {
    color: var(--text);
    font-size: 1.35rem;
}

.stat-item-warning {
    background: #fff9ef;
    border-color: #f2d49e;
}

.stat-item-warning .stat-value {
    color: var(--warning);
}

.stat-item-success {
    background: #f0fbf5;
    border-color: #b9e6c9;
}

.stat-item-success .stat-value {
    color: var(--success);
}

.cards-list {
    display: grid;
    gap: 16px;
}

.empty-state {
    padding: 28px 18px;
    border: 1px dashed var(--border);
    border-radius: 12px;
    text-align: center;
    color: var(--muted);
    background: #fafcff;
}

.card-item {
    border: 1px solid var(--border);
    border-radius: 14px;
    background: linear-gradient(180deg, #fff 0%, #fbfcff 100%);
    padding: 18px;
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 12px;
    gap: 12px;
}

.card-header h3 {
    margin: 0;
    font-size: 1.05rem;
}

.card-badge {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 6px 10px;
    border-radius: 999px;
    background: #eef5ff;
    color: var(--primary-dark);
    font-size: 12px;
    font-weight: 700;
}

.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 14px;
}

.language-block {
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 12px;
    background: #f9fbff;
}

.language-block h4 {
    margin-bottom: 8px;
    color: var(--muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    font-size: 11px;
}

.language-block p {
    margin-bottom: 10px;
    line-height: 1.5;
}

.option-list {
    margin: 0;
    padding-left: 0;
    list-style: none;
    display: grid;
    gap: 8px;
}

.option-list li {
    line-height: 1.5;
}

.answer-option {
    display: flex;
    align-items: flex-start;
    gap: 10px;
    cursor: default;
}

.answer-option input[type="radio"] {
    margin-top: 4px;
    accent-color: var(--success);
}

.answer-text {
    display: inline-block;
    border-radius: 8px;
    padding: 2px 6px;
}

.correct-option .answer-text {
    background: #ddf7e7;
    color: #0a6d3f;
    font-weight: 600;
}

.card-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-top: 12px;
    padding-top: 10px;
    border-top: 1px solid var(--border);
    color: var(--muted);
    font-size: 14px;
}

.card-meta strong {
    color: var(--text);
}

@media (max-width: 640px) {
    .app-shell {
        padding: 18px 12px 28px;
    }

    .panel {
        padding: 16px;
    }

    .control-row,
    .panel-header {
        flex-direction: column;
        align-items: stretch;
    }

    .control-row>* {
        width: 100%;
    }

    .stats-grid {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }
}

.language-switch {
    display: flex;
    gap: 16px;
    margin-bottom: 18px;
    color: var(--muted);
    font-weight: 700;
}

.language-switch input {
    accent-color: var(--primary);
}

.quiz-card {
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 20px;
    background: #f9fbff;
}

.quiz-card h3 {
    line-height: 1.45;
}

.quiz-options {
    display: grid;
    gap: 10px;
}

.quiz-answer {
    display: flex;
    gap: 10px;
    align-items: flex-start;
    padding: 12px;
    border: 1px solid var(--border);
    border-radius: 10px;
    background: #fff;
    cursor: pointer;
    transition: border-color 0.15s ease, background 0.15s ease, transform 0.15s ease;
}

.quiz-answer:hover {
    border-color: var(--primary);
    background: #f6f8ff;
    transform: translateY(-1px);
}

.quiz-answer input {
    margin-top: 4px;
    accent-color: var(--primary);
}

.quiz-answer.answer-correct {
    border-color: var(--success);
    background: #ddf7e7;
}

.quiz-answer.answer-wrong {
    border-color: var(--danger);
    background: #ffe2e6;
}

.quiz-actions {
    display: flex;
    justify-content: flex-end;
    margin-top: 18px;
}

.mistakes-review {
    margin-top: 18px;
    display: grid;
    gap: 16px;
}

.review-item {
    border: 1px solid var(--border);
    border-radius: 14px;
    background: #fff;
    padding: 16px;
}

.review-item h4 {
    margin-bottom: 12px;
}

.review-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 14px;
}

.review-language {
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 12px;
    background: #f9fbff;
}

.review-language h5 {
    margin-bottom: 8px;
    color: var(--muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    font-size: 11px;
}

.review-language p {
    margin-bottom: 12px;
    line-height: 1.5;
}

.review-options {
    list-style: none;
    margin: 0;
    padding: 0;
    display: grid;
    gap: 8px;
}

.review-option {
    display: block;
    padding: 8px 10px;
    border-radius: 8px;
    border: 1px solid var(--border);
    background: #fff;
}

.review-option.correct {
    background: #ddf7e7;
    border-color: var(--success);
    color: #0a6d3f;
    font-weight: 700;
}

.review-option.wrong {
    background: #ffe2e6;
    border-color: var(--danger);
    color: #8d1c2d;
    font-weight: 700;
}

.review-option.selected-label {
    font-weight: 700;
}

.review-empty {
    padding: 16px;
    border: 1px dashed var(--border);
    border-radius: 12px;
    background: #fafcff;
    color: var(--muted);
}