* {
    box-sizing: border-box;
    font-family: 'Nunito', sans-serif;
}

html,
body {
    margin: 0;
    padding: 0;
}

body {
    background-color: #14bdac;
    display: grid;
    place-items: center;
    min-height: 100vh;
}


.board {
    display: grid;
    grid-template-columns: repeat(3, auto);
    gap: 0.5rem;
    background-color: #0DA192;
}

.square {
    height: 7rem;
    width: 7rem;
    background-color: #14bdac;
    border: none;
    font-size: 3rem;
    font-weight: bold;
    color: #fff;
    transition: font-size 200ms cubic-bezier(0.175, 0.885, 0.32, 1.275);
    will-change: font-size;
}

.square:active {
    font-size: 4.2rem;
}

.overlay {
    background: rgba(0, 0, 0, 0.4);
    height: 100vh;
    width: 100vw;
    position: fixed;
    display: none;
    place-items: center;
}

.popup {
    width: min(100% - 2rem, 28rem);
    height: min(100% - 2rem, 32rem);
    border-radius: 1rem;
    background-color: #fff;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    animation: zoomIn 300ms ease-in-out;
}

.popup__header {
    padding-top: 2rem;
    height: 12rem;
    background-color: #0DA192;
    border-radius: 1rem 1rem 0 0;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.popup__header h1 {
    font-size: 2.1rem;
    margin: 0;
    font-weight: 800;
    color: hsl(174, 85%, 20%);
}


.popup__footer {
    padding: 0 2rem 2rem 2rem;
    text-align: center;
}


.btn {
    align-items: center;
    appearance: none;
    background-image: radial-gradient(100% 100% at 100% 0, #5adaff 0, #14bdac 100%);
    border: 0;
    border-radius: 0.6rem;
    box-shadow: rgba(45, 35, 66, .4) 0 2px 4px, rgba(45, 35, 66, .3) 0 7px 13px -3px, rgba(58, 65, 111, .5) 0 -3px 0 inset;
    box-sizing: border-box;
    color: rgba(0, 0, 0, 0.7);
    cursor: pointer;
    display: inline-flex;
    font-weight: 700;
    min-height: 3rem;
    justify-content: center;
    outline: none;
    overflow: hidden;
    padding-left: 2rem;
    padding-right: 2rem;
    position: relative;
    text-align: left;
    text-decoration: none;
    transition: box-shadow .15s, transform .15s;
    user-select: none;
    -webkit-user-select: none;
    touch-action: manipulation;
    white-space: nowrap;
    width: 100%;
    will-change: box-shadow, transform;
    font-size: 1.2rem;
}

.btn:focus {
    box-shadow: #0DA192 0 0 0 1.5px inset, rgba(45, 35, 66, .4) 0 2px 4px, rgba(45, 35, 66, .3) 0 7px 13px -3px, #0DA192 0 -3px 0 inset;
}

.btn:hover {
    box-shadow: rgba(45, 35, 66, .4) 0 4px 8px, rgba(45, 35, 66, .3) 0 7px 13px -3px, #0DA192 0 -3px 0 inset;
    transform: translateY(-2px);
}

.btn:active {
    box-shadow: #0DA192 0 3px 7px inset;
    transform: translateY(2px);
}

@keyframes zoomIn {
    from {
        opacity: 0;
        transform: scale3d(0.3, 0.3, 0.3);
    }

    50% {
        opacity: 1;
    }
}