@font-face {
    font-family: "Sixteen Segments";
    src: url("./fonts/SixteenSegments.woff2") format("woff2"),
         url("./fonts/SixteenSegments.woff") format("woff"),
         url("./fonts/SixteenSegments.ttf") format("truetype")
}

html {
    --digi-green: #79ff54;
    --dark-green: #094909;
    --light-text: #eee;
    --dark-text: #111;
    --dark-trans: rgba(17, 17, 17, 0.9);
}

body {
    background-image: url("./images/matrix-356024_1920.jpg");
    background-size: cover;
    background-attachment: fixed;
    font-family: "Fira Sans", sans-serif;
    display: flex;
    text-align: center;
    flex-direction: column;
    margin: 0;
    padding: 0;
    min-height: 100vh;
    max-width: 100vw;
    background-color: var(--dark-green);
    color: var(--light-text);
}

header {
    flex: 0 0 auto;
    padding: 15px 0;
    background-color: var(--dark-trans);
}

header h1 {
    font-size: 70px;
    letter-spacing: 5px;
    margin: 0;
    color: var(--light-text);
}

main {
    flex: 1;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.calculator {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-template-rows: auto;
    grid-gap: 5px;
    background-color: #594859;
    padding: 10px;
    box-shadow: 1px 2px 10px 1px #222;
    border: 5px solid;
    border-color: #bbb #888 #666 #aaa;
    border-radius: 5px;
    max-width: 415px;
}

.display {
    grid-column: 1 / span 4;
    height: 150px;
    padding: 5px;
    overflow: hidden;
    background-color: #333;
    color: #1bff07;
    font-family: "Sixteen Segments", monospace;
    text-align: right;
    border: 1px solid #222;
    box-shadow: inset 0 0 5px rgba(0, 0, 0, 0.3); 
    display: flex;
    flex-direction: column;
}
.top-screen {
    height: 40%;
    font-size: 30px;
    max-width: 415px;
    overflow: hidden;
}
.main-screen {
    height: 60%;
    font-size: 70px;
    max-width: 415px;
    overflow: hidden;
}

button {
    font-family: "Fira Sans", sans-serif;
    height: 100px;
    width: 100px;
    font-size: 50px;
    text-align: center;
    border-color: var(--light-text);
    border-radius: 5px;
    box-shadow: 1px 2px 10px 1px #222;
    color: var(--dark-text);
    cursor: pointer;
}

button:hover {
    filter: brightness(.9);
}

button:active, .active {
    filter: brightness(.9);
    border: 1px solid #888; 
    box-shadow: inset 0 0 5px rgba(0, 0, 0, 0.3); 
}

.tooltip .tooltiptext {
    visibility: hidden;
    position: absolute;
    bottom: 115%;
    left: 0%;
    z-index: 1;

    width: 120px;
    font-size: 20px;
    background-color: var(--dark-green);
    border: 1px solid var(--digi-green);
    color: var(--light-text);
    opacity: 0;
    transition: opacity 0.7s;
    padding: 5px;
    border-radius: 5px;
}

/* Tooltip arrow */
.tooltip .tooltiptext::after {
    content: "";
    position: absolute;
    top: 100%;
    left: 50%;
    margin-left: -5px;
    border-width: 5px;
    border-style: solid;
    border-color: var(--digi-green) transparent transparent transparent;
  }

.tooltip:hover .tooltiptext, .tooltip:focus .tooltiptext {
    visibility: visible;
    opacity: 1;
}

.num, .plus-minus {
    background-color: #d9e1f2;
}

.clear {
    background-color: #f98383;
}

.operator {
    background-color: #ffff69;
}

.equal {
    grid-column: span 2;
    width: 205px;
    background-color: var(--digi-green);
}

footer {
    flex: 0 0 auto;
    padding: 10px;
    background-color: var(--dark-trans);
    letter-spacing: 2px;
}

footer a {
    color: var(--digi-green);
}

footer a:hover, footer a:focus {
    color: rgb(170, 255, 0);
    text-decoration: none;
    margin: 0;
}

@media screen and (max-width: 600px) {
    header h1 {
        font-size: (calc(70px *.75));
    }

    .calculator {
        max-width: calc(415px * .75);
        grid-gap: calc(5px * .75);
    }

    .display {
        max-width: calc(415px * .75);
        height: calc(150px * .75);
    }

    .top-screen {
        max-width: calc(415px * .75);
        font-size: calc(30px *.75);
    }

    .main-screen {
        max-width: calc(415px * .75);
        font-size: calc(70px * .75);
    }

    button {
        width: calc(100px * .75);
        height: calc(100px * .75);
        font-size: calc(50px *.75);
    }

    .equal {
        width: calc(205px * .75)
    }
}