/* Ubuntu 24.04 Basic–inspired calculator (proportions, not pixel-perfect) */

:root {
    --calc-bg: #242424;
    --calc-surface: #1e1e1e;
    --calc-display: #1a1a1a;
    --calc-key: #363636;
    --calc-key-hover: #454545;
    --calc-key-press: #2c2c2c;
    --calc-key-digit: #545454;
    --calc-key-digit-hover: #686868;
    --calc-key-digit-press: #484848;
    --calc-text: #f2f2f2;
    --calc-muted: #8a8a8a;
    --calc-equals: #e66100;
    --calc-equals-hover: #f37318;
    --calc-equals-press: #c85500;
    --calc-error: #c0c0c0;
    --calc-gap: 0.35rem;
    --calc-radius: 0.45rem;
    --calc-font: "Cantarell", "Ubuntu", "Noto Sans", sans-serif;
}

*,
*::before,
*::after {
    box-sizing: border-box;
}

body {
    margin: 0;
    min-height: 100vh;
    background: #d9d9d9;
    font-family: var(--calc-font);
    color: var(--calc-text);
}

.calculator {
    width: min(22rem, 100vw);
    min-height: 100vh;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    background: var(--calc-bg);
    box-shadow: 0 0.5rem 1.5rem rgba(0, 0, 0, 0.25);
}

.calculator__toolbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 0.5rem;
    padding: 0.55rem 0.75rem;
    background: var(--calc-surface);
    border-bottom: 1px solid #111;
}

.calculator__toolbar-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    border: 0;
    background: transparent;
    color: var(--calc-muted);
    font: inherit;
    font-size: 0.95rem;
    cursor: not-allowed;
    opacity: 0.75;
}

.calculator__toolbar-btn--disabled {
    color: var(--calc-muted);
}

.calculator__undo-icon {
    font-size: 1rem;
    line-height: 1;
}

.calculator__mode {
    margin-left: auto;
    margin-right: auto;
}

.calculator__mode-chevron {
    font-size: 0.75rem;
}

.calculator__display {
    flex: 1 1 auto;
    min-height: 10rem;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    padding: 0.75rem 1rem 0.5rem;
    background: var(--calc-display);
    border-bottom: 1px solid #111;
}

.calculator__history {
    flex: 1 1 auto;
    overflow-y: auto;
    text-align: right;
    font-size: 0.95rem;
    color: var(--calc-muted);
    line-height: 1.45;
    white-space: pre-wrap;
    word-break: break-all;
}

.calculator__history-line {
    display: block;
}

.calculator__field {
    min-height: 2rem;
    text-align: right;
    font-size: 1.65rem;
    font-weight: 500;
    letter-spacing: 0.01em;
    word-break: break-all;
}

.calculator__error {
    min-height: 1.25rem;
    margin-top: 0.25rem;
    text-align: right;
    font-size: 0.9rem;
    color: var(--calc-error);
}

.calculator__error[hidden] {
    display: none;
}

.calculator__keys {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    grid-template-rows: repeat(5, minmax(3.1rem, 1fr));
    gap: var(--calc-gap);
    padding: 0.55rem;
    background: var(--calc-bg);
}

.calculator__key {
    appearance: none;
    border: 0;
    border-radius: var(--calc-radius);
    background: var(--calc-key);
    color: var(--calc-text);
    font: inherit;
    font-size: 1.15rem;
    cursor: pointer;
    user-select: none;
    transition: background-color 80ms ease;
}

.calculator__key:hover {
    background: var(--calc-key-hover);
}

.calculator__key:active {
    background: var(--calc-key-press);
}

.calculator__key--digit {
    background: var(--calc-key-digit);
    font-weight: 700;
}

.calculator__key--digit:hover {
    background: var(--calc-key-digit-hover);
}

.calculator__key--digit:active {
    background: var(--calc-key-digit-press);
}

.calculator__key--square {
    font-style: italic;
}

.calculator__key--equals {
    grid-column: 5;
    grid-row: 4 / span 2;
    background: var(--calc-equals);
    font-size: 1.5rem;
    font-weight: 600;
}

.calculator__key--equals:hover {
    background: var(--calc-equals-hover);
}

.calculator__key--equals:active {
    background: var(--calc-equals-press);
}