:root {
    /* Light Mode (Default) */
    --bg: #ffffff;
    --text: #1a1a1a;
    --text-muted: #555555;
    --accent: #2c5282;
    /* Navy */
    --border: #e2e8f0;
    --link-hover: #0056b3;
    --card-bg: #ffffff;
    --tag-bg: #f7fafc;

    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
    --max-width: 1200px;
    /* Broadened to full web width */
}

[data-theme="dark"] {
    --bg: #111111;
    --text: #eeeeee;
    --text-muted: #aaaaaa;
    --accent: #63b3ed;
    /* Light Blue */
    --border: #333333;
    --link-hover: #90cdf4;
    --card-bg: #1a1a1a;
    --tag-bg: #222222;
}

* {
    box-sizing: border-box;
}

body {
    background-color: var(--bg);
    color: var(--text);
    font-family: var(--font-sans);
    line-height: 1.6;
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 2rem 2rem;
    transition: background-color 0.3s ease, color 0.3s ease;
}

a {
    color: var(--accent);
    text-decoration: none;
    border-bottom: 1px solid transparent;
    transition: all 0.2s ease;
}

a:hover {
    color: var(--link-hover);
    border-bottom-color: var(--link-hover);
}

/* Header */
header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 3rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--border);
}

.header-content h1 {
    font-size: 2rem;
    font-weight: 700;
    margin: 0 0 0.5rem 0;
    letter-spacing: -0.5px;
}

.header-content p {
    color: var(--text-muted);
    font-size: 1.1rem;
    margin: 0;
}

/* Theme Toggle */
.theme-toggle {
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text);
    padding: 0.5rem;
    border-radius: 50%;
    transition: background 0.2s;
}

.theme-toggle:hover {
    background: var(--border);
}

.theme-toggle svg {
    width: 20px;
    height: 20px;
    fill: none;
    stroke: currentColor;
    stroke-width: 2;
    stroke-linecap: round;
    stroke-linejoin: round;
}

/* Intro */
.intro {
    display: flex;
    gap: 3rem;
    margin-bottom: 4rem;
    align-items: center;
}

.profile-img {
    width: 140px;
    height: 140px;
    border-radius: 50%;
    object-fit: cover;
    flex-shrink: 0;
    border: 3px solid var(--border);
}

@media (max-width: 650px) {
    .intro {
        flex-direction: column-reverse;
        gap: 1.5rem;
        text-align: center;
    }
}

/* Research Box */
.research-box {
    margin-top: -2rem;
    margin-bottom: 4rem;
    padding: 1.5rem;
    background: var(--tag-bg);
    border-left: 4px solid var(--accent);
    border-radius: 4px;
}

.research-label {
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--accent);
    font-weight: 700;
    margin-bottom: 0.5rem;
    display: block;
}

.research-title {
    font-weight: 700;
    font-size: 1.1rem;
    margin-bottom: 0.5rem;
    display: block;
    color: var(--text);
}

.research-desc {
    color: var(--text-muted);
    font-size: 0.95rem;
    margin-bottom: 0.5rem;
    line-height: 1.5;
}

.research-link {
    font-size: 0.9rem;
    font-weight: 600;
}

/* Projects Grid */
h2 {
    font-size: 1.5rem;
    font-weight: 700;
    margin-top: 4rem;
    margin-bottom: 1.5rem;
    color: var(--text);
    border-bottom: 2px solid var(--border);
    padding-bottom: 0.5rem;
    display: inline-block;
}

.project-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 1.5rem;
}

.project-card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    padding: 1.5rem;
    border-radius: 8px;
    transition: transform 0.2s, box-shadow 0.2s;
}

.project-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 6px 15px rgba(0, 0, 0, 0.08);
}

.project-header {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    margin-bottom: 0.75rem;
}

.project-title {
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--text);
    border-bottom: none !important;
}

.project-desc {
    font-size: 0.95rem;
    color: var(--text-muted);
    margin-bottom: 1.25rem;
    line-height: 1.5;
}

.project-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.tag {
    font-size: 0.75rem;
    padding: 0.25rem 0.6rem;
    background: var(--tag-bg);
    border-radius: 20px;
    color: var(--text-muted);
    font-weight: 500;
    border: 1px solid var(--border);
}

.project-links a {
    font-size: 0.9rem;
    margin-right: 1rem;
    font-weight: 600;
}

/* Skills */
.skill-category {
    margin-bottom: 2rem;
}

.skill-category h3 {
    font-size: 1rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 1rem;
    color: var(--text-muted);
    font-weight: 600;
}

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.8rem;
}

.skill-tag {
    font-size: 0.9rem;
    padding: 0.4rem 0.8rem;
    background: var(--tag-bg);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text);
    font-weight: 500;
}

/* Footer */
footer {
    margin-top: 5rem;
    padding-top: 2rem;
    border-top: 1px solid var(--border);
    color: var(--text-muted);
    font-size: 0.9rem;
    text-align: center;
}