body {
    font-family: Open Sans, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #F7F7F7;
}

header {
    background-color: #2E865F;
    color: #fff;
    padding: 1em;
    text-align: center;
}

nav ul {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: space-between;
}

nav li {
    margin-right: 20px;
}

nav a {
    color: #8BC34A;
    text-decoration: none;
}

nav a:hover {
    color: #fff;
}

main {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 2em;
    background-color: #F7F7F7;
}

h1 {
    color: #2E865F;
    font-weight: bold;
}

button {
    background-color: #2E865F;
    color: #fff;
    border: none;
    padding: 10px 20px;
    font-size: 22px;
    cursor: pointer;
}

button:hover {
    background-color: #8BC34A;
}

.responsive-banner {
	margin: 10px auto;
	width: 0%;
	min-width: 550px;
	max-width:550px;
	position: relative;
	height: auto;
	min-height:500p;
	max-height: 600px;
	border-radius: 10px;
	overflow: hidden;
	background-image: linear-gradient(to bottom right, #D45BA1, #A784E0);
}
.container-envelope {
	padding: 10px 5px;
	color: #fff;
}
img {
	max-width : 1024px;
	width: 100%;
	position: center;
}
span:after,
span:before {
	content: "";
	position: absolute;
	display: block;
	border-radius: 50%;
	background-color: rgba(0, 0, 0, 0.1);
	width: 150px;
	height: 150px;
}
.circle-a:before {
	width: 500px;
	height: 500px;
	top: -30px; left: 52%;
	-webkit-transform: translate(-50%,0);
	-ms-transform: translate(-50%,0);
	transform: translate(-50%,0);
}
.circle-a:after {
	top: 600px;
	right: 10%;
}
.circle-b:before {
	top: 60%;
	left: -25px;
}
.circle-b:after {
	width: 600px;
	height: 150px;
	bottom: -70px;
	right: -10px;
}