:root {
    --tg-theme-bg-color: #ffffff;
    --tg-theme-text-color: #1c1c1e;
    --tg-theme-hint-color: #8e8e93;
    --tg-theme-button-color: #3390ec;
    --tg-theme-button-text-color: #ffffff;
    --tg-theme-secondary-bg-color: #f2f2f7;
}

html, body {
    margin: 0;
    padding: 0;
    font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
    background: var(--tg-theme-bg-color);
    color: var(--tg-theme-text-color);
    -webkit-tap-highlight-color: transparent;
}

.twa-header {
    margin-bottom: 1rem;
}

.twa-title {
    margin: 0;
    font-size: 1.35rem;
    font-weight: 600;
}

.twa-subtitle {
    margin: 0.35rem 0 0;
    font-size: 0.85rem;
    color: var(--tg-theme-hint-color);
}

.twa-footnote {
    margin: 1rem 0 0;
    font-size: 0.75rem;
    text-align: center;
    color: var(--tg-theme-hint-color);
}

.calc-display {
    display: block;
    width: 100%;
    box-sizing: border-box;
    text-align: right;
    font-size: clamp(2rem, 10vw, 3rem);
    font-weight: 300;
    padding: 0.75rem 0.5rem 1.25rem;
    border: none;
    background: transparent;
    color: var(--tg-theme-text-color);
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.calc-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0.55rem;
}

.calc-btn {
    border: none;
    border-radius: 999px;
    min-height: 3.25rem;
    font-size: 1.35rem;
    font-weight: 500;
    cursor: pointer;
    background: var(--tg-theme-secondary-bg-color);
    color: var(--tg-theme-text-color);
    transition: transform 0.08s ease, opacity 0.08s ease;
    user-select: none;
    -webkit-user-select: none;
}

.calc-btn:active {
    transform: scale(0.96);
    opacity: 0.85;
}

.calc-fn {
    color: var(--tg-theme-text-color);
    background: var(--tg-theme-secondary-bg-color);
    filter: brightness(0.97);
}

.calc-op {
    background: var(--tg-theme-button-color);
    color: var(--tg-theme-button-text-color);
}

.calc-eq {
    background: var(--tg-theme-button-color);
    color: var(--tg-theme-button-text-color);
}

.calc-zero {
    grid-column: span 2;
    text-align: left;
    padding-left: 1.4rem;
}