body {
    background:#1d2125;
    color: #fff;
    font-family: Helvetica, sans-serif;
    margin: 0;
}

h2 {
    font-size: 30px;
    line-height: 32px;
}

h3 {
    font-size: 26px;
}

h4 {
    font-size: 32px;
    font-weight: 100;
    margin-top: -16px;
    margin-bottom: 16px;
}

.container {
    width: 100%;
    max-width: 1100px;
    margin: 0 auto;
}

/*** header ***/
header {
    background: #24292d;
    height: 80px;
    display: flex;
    align-items: center;
    padding: 0 16px;
}

.hamburger {
    display: flex;
    width: 30px;
    height: 30px;
    flex-direction: column;
    justify-content: space-between;
    margin-right: 24px;
}

.hamburger div {
    width: 30px;
    height: 5px;
    background: #fff;
    border-radius: 5px;
}

header img{
    width: 180px;
}

nav {
    display: none;
}

nav a {
    color: #fff;
    text-decoration: none;
    margin-left: 16px;
}

/*** welcome container ***/
.welcome-container .container {
    padding: 100px 16px;
    display: flex;
    flex-direction: column;
    box-sizing: border-box;
}

.welcome-container img {
    width: 100%;
}

.welcome-container div {
    text-align: center;
}

/*** challenges section ***/
.challenges-container {
    background: #fff;
    color: #000;
    text-align: center;
    padding: 24px;
}

.challenges {
    display: flex;
    flex-wrap: wrap;
}

.challenges a {
    background: #fafafa;
    border: 2px solid #24292d;
    border-radius: 16px;
    width: 100%;
    text-decoration: none;
    color: #000;
    box-shadow: 12px 12px 0 0 #d8eee6;
    padding: 16px;
    margin-bottom: 32px;
}

.challenges a div {
    border: 2px solid #d8eee6;
    border-radius: 16px;
}

.challenges a img {
    width: 80%;
}

.circles {
    display: flex;
    justify-content: space-between;
    margin: 16px;
    margin-bottom: -16px;
}

.circles span {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: #ec4342;
}

.circles span:last-child {
    background: #5583c3;
}

/*** media queries ***/
@media (min-width: 650px) {
    header {
        justify-content: space-between;
    }

    nav {
        display: inline-block;
    }

    .hamburger {
        display: none;
    }

    .welcome-container div {
        text-align: left;
    }
}

@media (min-width: 900px) {
    .welcome-container .container {
        flex-direction: row;
        align-items: center;
    }

    .welcome-container img{
        width: 50%;
    }

    .challenges a {
        width: 25%;
        flex-grow: 1;
        margin: 16px;
    }
}