@import url('https://fonts.googleapis.com/css2?family=Poppins:ital,wght@0,100;0,200;0,300;0,400;0,500;0,600;0,700;0,800;0,900;1,100;1,200;1,300;1,400;1,500;1,600;1,700;1,800;1,900&display=swap');


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

body {
    font-family: Poppins, sans-serif;
    background-color: #333;
    color: #eee;
}

.btn {
    border: none;
    border-radius: 10px;
    background-color: hsl(270, 45%, 35%);
    color: #eee;
    padding: 0.7rem 1.3rem;
    font-size: 1.1rem;
}

.wrapper {
    height: 100vh;
    max-width: 1200px;
    margin: 0 auto;
    padding-inline: 2rem;

    display: flex;
    flex-direction: column;
    align-items: center;
}

.header {
    display: flex;
    justify-content: space-around;
    align-items: center;
    flex-wrap: wrap;
    width: 100%;
    padding-block: 2rem;
}

.top-nav-container {
    position: relative;
}

.top-nav {
    background-color: #222;
    padding: 1.5rem;
    border-radius: 8px;

    position: absolute;
    top: 150%;
    left: 0;

    display: flex;
    flex-direction: column;
    gap: 1rem;

    opacity: 0;
    z-index: -5;
    transition: opacity 200ms ease-out;
}

.top-nav-opacity {
    opacity: 1;
    z-index: 2;
}

#top-nav-btn-menu {
    background-color: hsl(246, 48%, 32%);
}

.welcome {
    padding-top: 5rem;
    text-align: center;
    max-width: 300px;
}

.level-nav-container {
    margin-top: 3rem;
}

.level-nav {
    display: flex;
    gap: 2rem;
    flex-wrap: wrap;
}

.math-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
    padding: 2rem;
    margin-top: 5rem;
}

#math-problem {
    font-size: 8rem;
    font-weight: 300;
}

#btn-next {
    font-size: 1rem;
    padding: 0.8rem 1.5rem;
    display: flex;
    align-items: center;
    gap: 1rem;
    background-color: hsl(166, 58%, 24%);
}

.hidden {
    display: none;
}

@media (width < 768px) {

    .math-container {
        justify-content: space-around;
    }

    #math-problem {
        font-size: 5rem;
    }
}