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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--tg-theme-bg-color, #ffffff);
    color: var(--tg-theme-text-color, #000000);
    min-height: 100vh;
    padding-bottom: 20px;
}

#app {
    max-width: 480px;
    margin: 0 auto;
    padding: 16px;
}

.loading {
    text-align: center;
    padding: 60px 20px;
    font-size: 18px;
    color: var(--tg-theme-hint-color, #999);
}

/* ===== Header ===== */
.header {
    text-align: center;
    padding: 16px 0 20px;
}

.header h1 {
    font-size: 22px;
    font-weight: 700;
}

.header p {
    font-size: 14px;
    color: var(--tg-theme-hint-color, #999);
    margin-top: 4px;
}

.breadcrumb {
    font-size: 13px;
    color: var(--tg-theme-hint-color, #999);
    margin-bottom: 12px;
}

/* ===== Buttons / Cards ===== */
.btn-list {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.btn {
    display: block;
    width: 100%;
    padding: 14px 16px;
    border: none;
    border-radius: 12px;
    font-size: 16px;
    font-weight: 500;
    text-align: left;
    cursor: pointer;
    transition: transform 0.1s, opacity 0.1s;
    background: var(--tg-theme-secondary-bg-color, #f0f0f0);
    color: var(--tg-theme-text-color, #000);
}

.btn:active {
    transform: scale(0.98);
    opacity: 0.8;
}

.btn-primary {
    background: var(--tg-theme-button-color, #3390ec);
    color: var(--tg-theme-button-text-color, #fff);
    text-align: center;
}

.btn-disabled {
    opacity: 0.5;
    pointer-events: none;
}

.btn-danger {
    background: #e74c3c;
    color: #fff;
    text-align: center;
}

.btn-icon {
    margin-right: 8px;
}

.btn-hint {
    font-size: 12px;
    color: var(--tg-theme-hint-color, #999);
    margin-top: 2px;
    font-weight: 400;
}

/* ===== Question Card ===== */
.question-card {
    background: var(--tg-theme-secondary-bg-color, #f7f7f7);
    border-radius: 16px;
    padding: 20px;
    margin-bottom: 16px;
}

.question-number {
    font-size: 13px;
    color: var(--tg-theme-hint-color, #999);
    margin-bottom: 8px;
}

.question-text {
    font-size: 16px;
    line-height: 1.5;
    margin-bottom: 16px;
}

.options-list {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.option-btn {
    display: block;
    width: 100%;
    padding: 12px 16px;
    border: 2px solid var(--tg-theme-secondary-bg-color, #e0e0e0);
    border-radius: 10px;
    font-size: 15px;
    text-align: left;
    cursor: pointer;
    background: var(--tg-theme-bg-color, #fff);
    color: var(--tg-theme-text-color, #000);
    transition: all 0.15s;
    line-height: 1.4;
}

.option-btn:active {
    transform: scale(0.98);
}

.option-btn.selected {
    border-color: var(--tg-theme-button-color, #3390ec);
    background: rgba(51, 144, 236, 0.1);
}

.option-btn.correct {
    border-color: #27ae60;
    background: rgba(39, 174, 96, 0.1);
}

.option-btn.wrong {
    border-color: #e74c3c;
    background: rgba(231, 76, 60, 0.1);
}

.option-btn.correct-highlight {
    border-color: #27ae60;
    background: rgba(39, 174, 96, 0.15);
}

.option-number {
    display: inline-block;
    width: 24px;
    font-weight: 600;
}

/* ===== Timer Bar ===== */
.timer-bar {
    position: sticky;
    top: 0;
    z-index: 100;
    background: var(--tg-theme-bg-color, #fff);
    padding: 10px 0;
    margin: -16px -16px 12px;
    padding: 10px 16px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--tg-theme-secondary-bg-color, #e0e0e0);
}

.timer-text {
    font-size: 16px;
    font-weight: 600;
}

.timer-text.warning {
    color: #e67e22;
}

.timer-text.danger {
    color: #e74c3c;
}

.timer-progress {
    font-size: 14px;
    color: var(--tg-theme-hint-color, #999);
}

/* ===== Result Card ===== */
.result-card {
    background: var(--tg-theme-secondary-bg-color, #f7f7f7);
    border-radius: 16px;
    padding: 24px;
    text-align: center;
    margin-bottom: 16px;
}

.result-score {
    font-size: 48px;
    font-weight: 700;
    margin: 12px 0;
}

.result-stats {
    font-size: 15px;
    line-height: 2;
    color: var(--tg-theme-hint-color, #666);
}

.result-stats span {
    color: var(--tg-theme-text-color, #000);
    font-weight: 600;
}

/* ===== Answer Feedback ===== */
.feedback-box {
    border-radius: 12px;
    padding: 16px;
    margin: 12px 0;
}

.feedback-correct {
    background: rgba(39, 174, 96, 0.1);
    border: 1px solid rgba(39, 174, 96, 0.3);
}

.feedback-wrong {
    background: rgba(231, 76, 60, 0.1);
    border: 1px solid rgba(231, 76, 60, 0.3);
}

.explanation {
    margin-top: 12px;
    padding: 12px;
    background: var(--tg-theme-secondary-bg-color, #f0f0f0);
    border-radius: 8px;
    font-size: 14px;
    line-height: 1.5;
}

/* ===== Review ===== */
.review-status {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 12px;
}

.review-nav {
    display: flex;
    gap: 8px;
    margin-top: 12px;
}

.review-nav .btn {
    flex: 1;
    text-align: center;
}

/* ===== Purchase ===== */
.price-tag {
    font-size: 14px;
    float: right;
    color: var(--tg-theme-hint-color, #999);
    font-weight: 400;
}

/* ===== Support ===== */
.support-textarea {
    width: 100%;
    min-height: 120px;
    padding: 12px;
    border: 2px solid var(--tg-theme-secondary-bg-color, #e0e0e0);
    border-radius: 12px;
    font-size: 15px;
    resize: vertical;
    background: var(--tg-theme-bg-color, #fff);
    color: var(--tg-theme-text-color, #000);
    margin-bottom: 12px;
    font-family: inherit;
}

.support-textarea:focus {
    outline: none;
    border-color: var(--tg-theme-button-color, #3390ec);
}

/* ===== Info box ===== */
.info-box {
    padding: 12px 16px;
    border-radius: 10px;
    margin-bottom: 12px;
    font-size: 14px;
}

.info-box.warning {
    background: rgba(230, 126, 34, 0.1);
    border: 1px solid rgba(230, 126, 34, 0.3);
}

.info-box.info {
    background: rgba(51, 144, 236, 0.1);
    border: 1px solid rgba(51, 144, 236, 0.3);
}

.info-box.success {
    background: rgba(39, 174, 96, 0.1);
    border: 1px solid rgba(39, 174, 96, 0.3);
}

/* ==================== Referral Screen ==================== */
.ref-balance-card {
    background: var(--tg-theme-secondary-bg-color, #1c1c1e);
    border-radius: 12px;
    padding: 16px;
    margin: 0 0 12px 0;
}
.ref-balance-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 6px 0;
    border-bottom: 1px solid rgba(255,255,255,0.06);
    font-size: 15px;
}
.ref-balance-row:last-child { border-bottom: none; }
.ref-balance-val {
    font-weight: 700;
    color: var(--tg-theme-button-color, #3390ec);
}

.ref-level-card {
    background: var(--tg-theme-secondary-bg-color, #1c1c1e);
    border-radius: 12px;
    padding: 16px;
    margin: 0 0 12px 0;
    text-align: center;
}
.ref-level-name {
    font-size: 20px;
    font-weight: 700;
    margin-bottom: 6px;
}
.ref-level-stats {
    font-size: 13px;
    opacity: 0.7;
    margin-bottom: 10px;
}
.ref-progress { margin-top: 10px; }
.ref-progress-label {
    font-size: 13px;
    margin-bottom: 6px;
    opacity: 0.8;
}
.ref-progress-bar {
    background: rgba(255,255,255,0.1);
    border-radius: 8px;
    height: 8px;
    overflow: hidden;
}
.ref-progress-fill {
    height: 100%;
    background: var(--tg-theme-button-color, #3390ec);
    border-radius: 8px;
    transition: width 0.4s;
}
.ref-progress-hint {
    font-size: 12px;
    opacity: 0.6;
    margin-top: 4px;
}

.ref-section-title {
    font-size: 13px;
    font-weight: 600;
    opacity: 0.6;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin: 16px 0 8px 0;
}

.ref-link-box {
    background: var(--tg-theme-secondary-bg-color, #1c1c1e);
    border-radius: 12px;
    padding: 12px 16px;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 8px;
    margin-bottom: 4px;
}
.ref-link-text {
    font-size: 13px;
    opacity: 0.7;
    word-break: break-all;
    flex: 1;
}
.ref-link-copy {
    font-size: 13px;
    color: var(--tg-theme-button-color, #3390ec);
    white-space: nowrap;
    font-weight: 600;
}

.ref-history {
    background: var(--tg-theme-secondary-bg-color, #1c1c1e);
    border-radius: 12px;
    overflow: hidden;
    margin-bottom: 4px;
}
.ref-op-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 16px;
    border-bottom: 1px solid rgba(255,255,255,0.06);
}
.ref-op-row:last-child { border-bottom: none; }
.ref-op-info { flex: 1; }
.ref-op-reason { font-size: 14px; }
.ref-op-date { font-size: 12px; opacity: 0.5; margin-top: 2px; }
.ref-op-delta { font-weight: 700; font-size: 16px; }
.ref-op-plus { color: #27ae60; }
.ref-op-minus { color: #e74c3c; }
.ref-history-empty { padding: 16px; text-align: center; opacity: 0.5; font-size: 14px; }

.ref-info-box {
    background: var(--tg-theme-secondary-bg-color, #1c1c1e);
    border-radius: 12px;
    padding: 14px 16px;
    font-size: 14px;
    line-height: 2;
    margin-bottom: 24px;
}