body,
ul,
li,
h1,
h2,
a {
    margin: 0;
    padding: 0;
    font-family: tahoma;
}
p {
    font-size: 18px;
}
header {
    background-color: #728308;
    padding: 20px 0;
    text-align: center;
    position: fixed;
    width: 100%;
    top: 0;
    left: 0;
    z-index: 1;
}
header h1 {
    color: white;
    border: 8px solid white;
    display: inline-block;
    padding: 6px 12px;
    border-radius: 36px;
}
.banner {
    position: relative;
}
.banner img {
    max-width: 100%;
    width: 100%;
}
.banner .welcome {
    background-color: rgba(255, 255, 255, 0.5);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-radius: 10px;
    border: 1px solid rgba(255, 255, 255, 0.5);
    color: white;
    padding: 30px;
    font-size: 60px;
    position: absolute;
    left: 0;
    top: 30%;
}
.banner .welcome span {
    font-size: 1.4em;
}
nav {
    background: #f4f4f4;
    padding: 20px;
    position: sticky;
    top: 106px;
    z-index: 1;
}
nav ul {
    white-space: nowrap;
    max-width: 1200px;
    margin: 0 auto;
    text-align: center;
}
nav li {
    width: 25%;
    display: inline-block;
    font-size: 24px;
}
nav li a {
    text-decoration: none;
    color: #4b4b4b;
}
nav li a:hover {
    text-decoration: underline;
}
nav li a.join {
    color: #728308;
}

main {
    max-width: 100%;
    width: 1200px;
    margin: 80px auto;
    padding: 0 40px;
    box-sizing: border-box;
}
article h2 {
    color: #728308;
    font-size: 48px;
}
article p {
    line-height: 2em;
    color: #4b4b4b;
}
article p::first-line {
    font-weight: bold;
    font-size: 1.2em;
}
.images {
    /* text-align: center; */
    margin: 80px 0;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
}

.images li {
    display: inline-block;
    list-style-type: none;
}

.images li img {
    max-width: 100%;
    transition: all 0.2s;
}

.images li img:hover {
    transform: scale(1.2);
}

section.join {
    background: #f4f4f4;
    text-align: center;
    padding: 60px 20px;
    color: #4b4b4b;
}
section.join h2 {
    font-size: 36px;
}
form input {
    margin: 20px 0;
    padding: 10px 20px;
    font-size: 24px;
    border-radius: 28px;
    border: 4px solid white;
}

form input:focus {
    border: 4px dashed #4b4b4b;
    outline: none;
}
form input:valid {
    border: 4px solid #71d300;
}
footer {
    background: #728308;
    color: white;
    padding: 10px;
    text-align: center;
}

/* responsive styles */

@media screen and (max-width: 1400px) {
    .banner .welcome {
        font-size: 40px;
    }
}

@media screen and (max-width: 960px) {
    .banner .welcome {
        font-size: 28px;
    }
    nav li {
        font-size: 18px;
    }
    .images li:nth-child(3) {
        grid-column: 3;
    }
    .images li:nth-child(2) {
        grid-column: 2 / 3;
        grid-row: 2 / 3;
    }
}

@media screen and (max-width: 700px) {
    p {
        font-size: 16px;
    }
    .banner .welcome {
        font-size: 20px;
        position: relative;
        text-align: center;
        padding: 20px;
        color: #4b4b4b;
    }
    .banner .welcome br {
        display: none;
    }
    .banner .welcome span {
        font-size: 1em;
    }
    nav li {
        font-size: 18px;
    }
}

@media screen and (max-width: 560px) {
    .banner .welcome {
        font-size: 20px;
        position: relative;
        text-align: center;
    }
    .banner .welcome br {
        display: none;
    }
    .banner .welcome span {
        font-size: 1em;
    }
    nav li {
        display: block;
        width: 100%;
        margin: 12px 0;
    }
    article h2 {
        font-size: 36px;
    }
    header,
    nav {
        position: relative;
        top: 0;
    }
}

@media screen and (max-width: 440px) {
    .images {
        display: flex;
        flex-direction: column;
        gap: 3rem;
    }
}