/* Modern CSS Reset */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

/* CSS Custom Properties */
:root {
    --primary-color: #003399;
    --secondary-color: #8888DD;
    --text-color: #2c2c2c;
    --background-color: #ffffff;
    --menu-width: 250px;
    --header-height: 60px;
    --content-max-width: 1200px;
    --spacing-unit: 1rem;
}

/* Base Layout */
.site-layout {
    min-height: 100vh;
    display: grid;
    grid-template-areas:
        "nav header"
        "nav main"
        "nav footer";
    grid-template-columns: var(--menu-width) 1fr;
    grid-template-rows: auto 1fr auto;
}

/* Container */
.site-container {
    display: contents; /* Allow children to participate in parent grid */
}

/* Header */
.site-header {
    grid-area: header;
    padding: var(--spacing-unit);
    background: var(--background-color);
    border-bottom: 1px solid rgba(0,0,0,0.1);
    z-index: 2;
}

.site-header h1 {
    color: var(--primary-color);
    font-size: 2rem;
    margin: 0;
}

/* Navigation */
.main-nav {
    grid-area: nav;
    position: fixed;
    width: var(--menu-width);
    height: 100vh;
    background: var(--background-color);
    box-shadow: 2px 0 8px rgba(0,0,0,0.1);
    overflow-y: auto;
    z-index: 1000;
}

/* Main Content */
.site-content {
    grid-area: main;
    padding: var(--spacing-unit);
    max-width: var(--content-max-width);
    margin: 0 auto;
    width: 100%;
    background: var(--background-color);
}

/* Footer */
.site-footer {
    grid-area: footer;
    padding: var(--spacing-unit);
    background: var(--secondary-color);
    text-align: center;
}

/* Responsive Layout */
@media (max-width: 767px) {
    .site-layout {
        grid-template-areas:
            "header"
            "nav"
            "main"
            "footer";
        grid-template-columns: 1fr;
        grid-template-rows: auto auto 1fr auto;
    }

    .main-nav {
        position: relative;
        width: 100%;
        height: auto;
        max-height: none;
    }

    .site-content {
        margin: 0;
        padding: var(--spacing-unit);
    }
}

/* Print styles */
@media print {
    .site-layout {
        display: block;
    }

    .main-nav {
        display: none;
    }

    .site-content {
        margin: 0;
        max-width: none;
    }
}