:root {
    --calc-bg: #303030;
    --calc-history-bg: #474747;
    --calc-input-bg: #3d3d3d;
    --calc-display-divider: #2b2b2b;
    --calc-key-digit-bg: #5e5e5e;
    --calc-key-digit-bg-hover: #656565;
    --calc-key-digit-bg-active: #545454;
    --calc-key-dark-bg: #454545;
    --calc-key-dark-bg-hover: #505050;
    --calc-key-dark-bg-active: #3d3d3d;
    --calc-key-equals-bg: #eb6536;
    --calc-key-equals-bg-hover: #ed744a;
    --calc-key-equals-bg-active: #bc512b;
    --calc-key-font-size: 1.125rem;
    --calc-key-size: calc(var(--calc-key-font-size) * 3 * 0.9);
    --calc-text: #ffffff;
    --calc-text-muted: #9a9a9a;
    --calc-inactive-color: #6e6e6e;
    --calc-display-text: #ffffff;
    --calc-error-color: #ff6b6b;
    --calc-error-zero-highlight-bg: #71493b;
    --calc-width: 391px;
    --calc-height: 533px;
    --calc-page-padding: 16px;
    --calc-keypad-gap: 3px;
    --calc-keypad-padding: 8px;
    --calc-font: "Cantarell", "Ubuntu", "Segoe UI", sans-serif;
}

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

body {
    margin: 0;
    background: #242424;
    color: var(--calc-text);
    font-family: var(--calc-font);
}

.calculator-page {
    min-height: 100vh;
    padding: var(--calc-page-padding);
    background: #242424;
    box-sizing: border-box;
}

.calculator-page--overflow {
    position: relative;
    padding: 0;
    min-height: max(100vh, calc(50vh + var(--calc-height) / 2));
    min-width: max(100%, calc(50vw + var(--calc-width) / 2));
}

.calculator-page--overflow .calculator {
    position: absolute;
    left: calc(50vw - var(--calc-width) / 2);
    top: calc(50vh - var(--calc-height) / 2);
}

.calculator {
    display: flex;
    flex-direction: column;
    width: var(--calc-width);
    height: var(--calc-height);
    background: var(--calc-bg);
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.35);
}

.calculator__header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 10px 14px 6px;
    min-height: 36px;
}

.calculator__control,
.calculator__mode {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    border: none;
    background: transparent;
    font-family: inherit;
    font-size: 0.875rem;
    font-weight: 700;
    line-height: 1;
    cursor: default;
    padding: 4px 0;
}

.calculator__control--inactive,
.calculator__mode--inactive {
    color: var(--calc-inactive-color);
}

.calculator__icon {
    flex-shrink: 0;
    display: block;
}

.calculator__icon--undo {
    opacity: 0.85;
}

.calculator__icon--chevron {
    margin-left: 4px;
}

.calculator__mode--dropdown {
    gap: 4px;
}

.calculator__display {
    display: flex;
    flex: 1 1 auto;
    flex-direction: column;
    margin-bottom: 4px;
    min-height: 0;
}

.calculator__display-panel {
    width: 100%;
    padding: 10px 14px;
    text-align: right;
}

.calculator__display-panel--history {
    flex: 1 1 auto;
    background: var(--calc-history-bg);
    color: var(--calc-text-muted);
    font-size: 0.875rem;
    line-height: 1.35;
    min-height: 72px;
    overflow-y: auto;
}

.calculator__display-divider {
    flex: 0 0 1px;
    height: 1px;
    background: var(--calc-display-divider);
}

.calculator__display-panel--input {
    flex: 0 0 auto;
    display: flex;
    flex-direction: column;
    justify-content: center;
    background: var(--calc-input-bg);
    min-height: 56px;
}

.calculator__history-entry {
    white-space: nowrap;
}

.calculator__history-equals {
    margin: 0 0.25em;
}

.calculator__error {
    color: var(--calc-error-color);
    font-size: 0.8125rem;
    margin-top: 4px;
}

.calculator__input-zero-highlight {
    background: var(--calc-error-zero-highlight-bg);
    border-radius: 2px;
}

.calculator__input {
    color: var(--calc-display-text);
    font-size: 1.75rem;
    line-height: 1.2;
    min-height: 2rem;
    word-break: break-all;
}

.calculator__keypad {
    flex: 0 0 auto;
    display: grid;
    grid-template-columns: repeat(5, minmax(0, 1fr));
    grid-auto-rows: var(--calc-key-size);
    gap: var(--calc-keypad-gap);
    padding: 0 var(--calc-keypad-padding) var(--calc-keypad-padding);
}

.calculator__key {
    border: none;
    border-radius: 10px;
    font: inherit;
    font-size: var(--calc-key-font-size);
    line-height: 1;
    cursor: default;
    color: var(--calc-text);
    background: var(--calc-key-dark-bg);
}

.calculator__key.key-digit,
.calculator__key.key-clear {
    font-weight: 700;
}

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

.calculator__key.key-function,
.calculator__key.key-clear,
.calculator__key.key-operator {
    font-size: 1rem;
}

.calculator__key.key-equals {
    background: var(--calc-key-equals-bg);
    color: var(--calc-text);
    font-size: 1.375rem;
}

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

.calculator__key--equals-span {
    grid-column: 5;
    grid-row: span 2;
    align-self: stretch;
}

.calculator__key:focus {
    outline: none;
}

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

.calculator__key.key-function:hover,
.calculator__key.key-clear:hover,
.calculator__key.key-operator:hover {
    background: var(--calc-key-dark-bg-hover);
}

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

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

.calculator__key.key-function:active,
.calculator__key.key-clear:active,
.calculator__key.key-operator:active {
    background: var(--calc-key-dark-bg-active);
}

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