:root {
    --font-family: 'Arial', sans-serif;
    
    /* Dark Mode (Default) - Updated Colors */
    --bg-color-dark: #0D1117; /* Very dark, almost black, slightly blue-ish */
    --card-bg-color-dark: #161B22; /* Dark gray, slightly blue-ish */
    --text-color-dark: #C9D1D9; /* Light gray for text */
    --primary-color-dark: #58A6FF; /* Bright blue for accents */
    --secondary-color-dark: #A371F7; /* Purple for secondary accents */
    --border-color-dark: #30363D; /* Medium gray for borders */
    --header-bg-dark: #161B22; /* Same as card background */

    /* Light Mode */
    --bg-color-light: #f0f2f5;
    --card-bg-color-light: #ffffff;
    --text-color-light: #333333;
    --primary-color-light: #4a90e2;
    --secondary-color-light: #d0021b;
    --border-color-light: #d1d1d1;
    --header-bg-light: #ffffff;

    /* Universal variables (can be overridden by theme) */
    --bg-color: var(--bg-color-dark);
    --card-bg-color: var(--card-bg-color-dark);
    --text-color: var(--text-color-dark);
    --primary-color: var(--primary-color-dark);
    --secondary-color: var(--secondary-color-dark);
    --border-color: var(--border-color-dark);
    --header-bg: var(--header-bg-dark);
    --shadow-color: rgba(0,0,0,0.2);
}

body {
    font-family: var(--font-family);
    margin: 0;
    background-color: var(--bg-color);
    color: var(--text-color);
    transition: background-color 0.3s ease, color 0.3s ease;
    line-height: 1.6;
}

body.light-mode {
    --bg-color: var(--bg-color-light);
    --card-bg-color: var(--card-bg-color-light);
    --text-color: var(--text-color-light);
    --primary-color: var(--primary-color-light);
    --secondary-color: var(--secondary-color-light);
    --border-color: var(--border-color-light);
    --header-bg: var(--header-bg-light);
    --shadow-color: rgba(0,0,0,0.1);
}

header {
    background-color: var(--header-bg);
    padding: 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color);
    transition: background-color 0.3s ease, border-bottom-color 0.3s ease;
    box-shadow: 0 2px 4px var(--shadow-color);
}

.profile-section {
    display: flex;
    align-items: center;
    flex-grow: 1; /* Allow profile section to take available space */
}

.profile-pic {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    object-fit: cover;
    margin-right: 20px;
    border: 2px solid var(--primary-color);
}

.bio {
    text-align: center; /* Center align the text within the bio */
    flex-grow: 1; /* Allow bio to take available space next to pic */
}

.bio h1 {
    margin-top: 0;
    margin-bottom: 5px;
    color: var(--primary-color);
    font-size: 1.8em;
}

.bio p {
    margin-bottom: 0;
    font-size: 0.9em;
    max-width: 600px;
    margin-left: auto; /* For centering block if max-width is hit */
    margin-right: auto; /* For centering block if max-width is hit */
}

.header-controls {
    display: flex;
    align-items: center;
    justify-content: flex-end; /* Align toggle to the right */
    flex-shrink: 0; /* Prevent shrinking if bio text is very long */
}

#theme-toggle {
    background: none;
    border: 1px solid var(--primary-color);
    color: var(--primary-color);
    font-size: 1.5em;
    cursor: pointer;
    padding: 8px 12px;
    border-radius: 50%;
    transition: background-color 0.3s, color 0.3s, transform 0.2s;
}

#theme-toggle:hover {
    background-color: var(--primary-color);
    color: var(--bg-color); /* Use bg-color for hover text to ensure contrast with primary */
    transform: scale(1.1);
}

.main-container {
    padding: 20px;
}

.content-area {
    flex-grow: 1;
}

.subject-cards-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr); /* Changed to 3 columns */
    gap: 20px;
}

.card {
    background-color: var(--card-bg-color);
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 4px 8px var(--shadow-color);
    transition: transform 0.3s ease, box-shadow 0.3s ease, background-color 0.3s ease;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

.card:hover {
    transform: translateY(-5px) scale(1.03);
    box-shadow: 0 8px 16px var(--shadow-color);
}

.card h2 {
    margin-top: 0;
    color: var(--primary-color);
    font-size: 1.5em;
}

.card p {
    font-size: 0.95em;
    flex-grow: 1;
    margin-bottom: 15px;
}

.btn-link {
    display: inline-block;
    background-color: var(--primary-color);
    color: var(--bg-color); /* Text color that contrasts well with primary_color */
    padding: 10px 15px;
    text-decoration: none;
    border-radius: 5px;
    text-align: center;
    font-weight: bold;
    transition: background-color 0.3s ease, transform 0.2s ease;
}

body.light-mode .btn-link {
    color: var(--card-bg-color-light); /* Ensure good contrast in light mode */
}
body.dark-mode .btn-link {
    color: #0D1117; /* Text color for buttons in dark mode, ensuring contrast with bright blue */
}

.btn-link:hover {
    background-color: var(--secondary-color);
    transform: scale(1.05);
}

/* Responsive Design */
@media (max-width: 1024px) {
    .subject-cards-grid {
        grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); /* Revert to auto-fit for smaller screens */
    }
}

@media (max-width: 768px) {
    header {
        flex-direction: column;
        align-items: center; /* Center items when stacked */
        gap: 15px; /* Add gap between stacked items */
    }

    .profile-section {
        flex-direction: column; /* Stack pic and bio */
        align-items: center; /* Center pic and bio */
        width: 100%; /* Take full width to center content */
        text-align: center; /* Ensure text inside is centered */
    }

    .profile-pic {
        margin-right: 0; /* Remove right margin */
        margin-bottom: 15px; /* Add bottom margin when stacked */
    }
    
    .bio {
        /* text-align: center; inherited from .profile-section or can be explicit */
        width: 100%; /* Ensure bio takes width for centering its content */
    }

    .bio h1 {
        font-size: 1.5em;
    }
    .bio p {
        font-size: 0.85em;
        max-width: 90%; /* Allow p to use more width and center nicely */
        /* margin-left/right: auto; will work due to max-width */
    }

    .header-controls {
        width: 100%;
        justify-content: center; /* Center toggle button */
    }
    
    #theme-toggle {
        /* position: absolute; top: 20px; right: 20px; removed */
        font-size: 1.3em; /* Keep existing responsive size */
    }

    .subject-cards-grid {
        grid-template-columns: 1fr; /* Single column */
    }
}

@media (max-width: 480px) {
    .bio h1 {
        font-size: 1.3em;
    }
     .bio p {
        font-size: 0.8em;
    }
    .card h2 {
        font-size: 1.3em;
    }
    .card p {
        font-size: 0.9em;
    }
    .btn-link {
        padding: 8px 12px;
        font-size: 0.9em;
    }
    #theme-toggle {
        padding: 6px 10px;
        font-size: 1.2em;
    }
}