styles.css

:root {
    --darkest: #022B3A;
    --dark: #1F7A8C;
    --button: #BFDBF7;
    --light: #E1E5F2;
    --lightest: #FFFFFF;
}

html {
    box-sizing: border-box;
}

body {
    box-sizing: border-box;
    font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    color: var(--darkest);
    background-color: var(--button);
    margin: 0;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    height: 100vh;
}

.flex-container {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100%;
}

#calc-body {
    font-family: "Audiowide", sans-serif;
    font-size: x-large;
    background-color: var(--darkest);
    border: 3px solid var(--dark);
    width: 300px !important;
    padding: 20px;
    border-radius: 5px;
    margin: 0 20px;
}

#screen {
    background-color: var(--lightest);
    font-size: x-large;
    text-align: right;
    padding: 10px 10px 10px 50px !important;
    margin-bottom: 20px;
    border-radius: 5px;
    display: flex;
    flex-direction: column;
}

#screen-equation, #screen-number {
    min-height: 50px;
    word-wrap: break-word;
    max-width: 100% !important;
}

#calc-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-gap: 10px 3px;
}

.span-2 {
    grid-column: span 2;
}

.span-4 {
    grid-column: span 4;
}

button {
    font-family: "Audiowide", sans-serif;
    font-size: x-large;
    outline: none;
    border: none;
    background-color: var(--button);
    width: 100%;
    height: 50px;
    border-radius: 5px;
    transition: 0.3s;
}

button:hover {
    background-color: var(--light) !important;
    
}

button:active {
    background-color: var(--dark) !important;
}

#ac {
    background-color: indianred;
}

#del {
    background-color: lightseagreen;
}

.operator, #equal-operator {
    background-color: lightyellow;
}

.footer {
    display: flex;
    align-items: center;
    background-color: var(--darkest);
    color: var(--lightest);
    justify-content: center;
    padding: 24px; 
}