/* 1. Foundational Styles & Variables */
:root {
    --font-family-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
    --font-color: #333;
    --link-color: #007acc;
    --link-hover-color: #00568f;
    --bg-color: #fff;
    --border-color: #ddd;
    --spacing-unit: 1rem;
}

*,
*::before,
*::after {
    box-sizing: border-box;
}

body {
    font-family: var(--font-family-sans);
    line-height: 1.6;
    color: var(--font-color);
    background-color: var(--bg-color);
    margin: 0;
    padding: calc(var(--spacing-unit) * 2);
}

/* 2. Mobile-First Layout (Default) */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-unit);
}

header img {
    max-width: 150px;
    height: auto;
    border-radius: 50%;
    display: block;
    margin: 0 auto var(--spacing-unit);
}

header h1 {
    text-align: center;
    margin: 0;
}

header p {
    text-align: center;
    margin: 0.25rem 0;
}

section {
    margin-bottom: calc(var(--spacing-unit) * 2);
}

h2 {
    border-bottom: 2px solid var(--border-color);
    padding-bottom: 0.5rem;
    margin-top: 0;
}

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

#courses ul li,
#publications ul li {
    margin-bottom: var(--spacing-unit);
    padding-left: 1.5rem;
    position: relative;
}

#courses ul li::before,
#publications ul li::before {
    content: '•';
    color: var(--link-color);
    position: absolute;
    left: 0;
    top: 0;
}

a {
    color: var(--link-color);
    text-decoration: none;
}

a:hover {
    color: var(--link-hover-color);
    text-decoration: underline;
}

footer {
    text-align: center;
    margin-top: calc(var(--spacing-unit) * 2);
    color: #777;
    font-size: 0.9rem;
}

/* 3. Responsive Layout for Larger Screens (Progressive Enhancement) */
@media (min-width: 768px) {
   .container {
        display: grid;
        grid-template-columns: 250px 1fr;
        grid-template-areas:
            "header main";
        gap: calc(var(--spacing-unit) * 3);
    }

    header {
        grid-area: header;
    }
    
    main {
        grid-area: main;
    }

    header img {
        margin-left: 0;
        margin-right: 0;
    }

    header h1,
    header p {
        text-align: left;
    }

    footer {
        grid-column: 1 / -1; /* Span footer across all columns */
    }
}