:root{
    --background: #c9c9c9;
    --text: #000000;
    --darker: #9d9d9d;
    --dark: #7a7a7a;
    --light: #f0f0f0;
    --lightest: #ffffff;
    --accent: #54775c;
}

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

main {
    font-family: Arial, Helvetica, sans-serif;
    max-width: 1200px;
    margin: 0 auto;
    padding: 25px;
}

body {
    background-color: var(--background);
    color: var(--text);
    line-height: 1.6;
}

header {
    text-align: center;
    padding: 20px;
    margin-bottom: 20px;
    background-color: var(--lightest);
    border-radius: 5px;
    box-shadow: 2px 2px 2px rgba(0,0,0,0.1);
}

header h1 {
    color: var(--accent);
    border-bottom: 7px dotted var(--accent);
    padding-bottom: 10px;
    display: inline-block;
}

nav {
    width: 80%;
    display: flex;
    justify-content: center;
    padding: 1rem;
    background-color: var(--darker);
    position: relative;
    box-shadow: 0 2px 10px #e5e5e5;
    margin: 0 auto 30px auto;
    border-radius: 5px;
}

nav a {
    margin: 0 10px;
    padding: 8px 15px;
    background-color: var(--dark);
    color: var(--light);
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s ease;
    text-decoration: none;
    font-size: 18px;
}

nav a:hover {
    background-color: var(--light);
    color: var(--dark);
    text-decoration: dotted overline;
}

.content-container {
    display: flex;
    flex-wrap: wrap;
    gap: 20px;
    margin-bottom: 30px;
}

.column {
    flex: 1;
    min-width: 300px;
    background-color: var(--lightest);
    padding: 20px;
    border-radius: 5px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    border-top: 5px solid var(--accent);
}

.column h2 {
    color: var(--accent);
    margin-bottom: 15px;
    border-bottom: 2px solid var(--accent);
    padding-bottom: 8px;
}

.column p {
    margin-bottom: 15px;
}

.schema-img {
    width: 100%;
    border: 1px solid var(--darker);
    margin-bottom: 15px;
}

ol, ul {
    margin-left: 20px;
    margin-bottom: 15px;
}

li {
    margin-bottom: 8px;
}

aside ul {
    list-style-type: none;
    margin-left: 0;
}

aside a {
    color: var(--accent);
    text-decoration: none;
    font-weight: bold;
}

aside a:hover {
    text-decoration: underline;
}

footer {
    text-align: center;
    padding: 15px;
    background-color: var(--darker);
    color: var(--light);
    border-radius: 5px;
    margin-top: 20px;
    clear: both;
}

@media screen and (max-width: 768px) {
    .content-container {
        flex-direction: column;
    }
    
    nav {
        flex-direction: column;
        align-items: center;
    }
    
    nav a {
        margin: 5px 0;
        width: 80%;
        text-align: center;
    }
    
    header h1 {
        font-size: 1.5rem;
    }
}