:root {
    --color-cream: #f6dbac;
    --color-teal: #018391;
    --color-teal-dark: #015e68;
    --color-orange: #ec8923;
    --color-orange-dark: #f15f2c;
    --color-red: #cd3333;
    --color-red-dark: #72231c;
    --color-screen-bg: #4a6368;
    --color-screen-border: #ffffff;
}

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

body {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100svh;
    font-family: "Orbitron", sans-serif;
}

button {
    font-family: inherit;
}

.calc {
    display: flex;
    flex-direction: column;
    gap: 60px;
    min-width: 350px;
    max-width: 350px;
    padding: 10px;
    background-color: var(--color-cream);
    border-radius: 12px;
}

.calc__header {
    display: flex;
    padding: 35px 20px;
    background-color: var(--color-teal);
    border-radius: 8px;
    box-shadow:
        0 4px var(--color-teal-dark),
        inset 0 2px 4px rgba(0, 0, 0, 0.2);
}

.calc__result {
    width: 100%;
    padding: 10px;
    font-size: 2rem;
    color: white;
    text-align: right;
    background-color: var(--color-screen-bg);
    border: 4px solid var(--color-screen-border);
    border-radius: 6px;
    box-shadow: inset 0 10px 10px rgba(0, 0, 0, 0.2);
}

.calc__keypad {
    display: flex;
    flex-direction: column;
    gap: 5px;
    padding: 10px;
}

.calc__row {
    display: flex;
    gap: 5px;
    list-style: none;
}

.calc__item {
    flex: 1;
}

.calc__btn {
    --_bg: var(--bg, var(--color-teal));
    --_shadow: var(--shadow, var(--color-teal-dark));

    width: 100%;
    padding: 22px;
    font-size: 1.2rem;
    color: white;
    cursor: pointer;
    background-color: var(--_bg);
    border: none;
    border-radius: 4px;
    box-shadow: 0 4px var(--_shadow);
    transition: transform 0.05s ease;
}

.calc__btn:active {
    box-shadow: inset 0 2px 3px rgba(0, 0, 0, 0.4);
    transform: translateY(1px);
}

.calc__btn--operator {
    --bg: var(--color-orange);
    --shadow: var(--color-orange-dark);
}

.calc__btn--function {
    --bg: var(--color-red);
    --shadow: var(--color-red-dark);
}