:root {
    --bg: #fafafa;
    --sidebar-bg: #1a1a1a;
    --sidebar-text: #e0e0e0;
    --text: #333;
    --accent: #6c5ce7;
    --accent-hover: #5a4bd1;
    --border: #ddd;
    --sidebar-width: 280px;
    --content-padding: 2.5rem;
    --sidebar-header-padding: 1.5rem;
    --link-padding: 0.75rem 1.5rem;
    --font-size-sm: 0.85rem;
    --font-size-base: 1rem;
    --font-size-h1: 1.8rem;
    --font-size-h2: 1.4rem;
    --font-size-h3: 1.1rem;
    --font-size-sidebar-title: 1.1rem;
    --transition-speed: 0.2s;
}

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

html, body {
    height: 100%;
}

body {
    font-family: 'Noto Sans Thai', sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
}

.skip-link {
    position: absolute;
    top: -100%;
    left: 0;
    background: var(--accent);
    color: #fff;
    padding: 0.75rem 1.5rem;
    z-index: 1000;
    font-size: var(--font-size-sm);
    text-decoration: none;
    transition: top var(--transition-speed);
}

.skip-link:focus {
    top: 0;
}

.container {
    display: flex;
    height: 100vh;
}

.sidebar {
    width: var(--sidebar-width);
    min-width: var(--sidebar-width);
    max-width: var(--sidebar-width);
    background: var(--sidebar-bg);
    color: var(--sidebar-text);
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.sidebar-header {
    padding: var(--sidebar-header-padding);
    border-bottom: 1px solid #333;
}

.sidebar-header h1 {
    font-size: var(--font-size-sidebar-title);
    font-weight: 600;
    color: #fff;
}

.sidebar-home {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 44px;
    height: 44px;
    margin: 1rem;
    border-radius: 8px;
    color: var(--sidebar-text);
    text-decoration: none;
    transition: background var(--transition-speed), color var(--transition-speed);
}

.sidebar-home:hover {
    background: #2a2a2a;
    color: #fff;
}

.sidebar-home:focus-visible {
    background: #2a2a2a;
    color: #fff;
    box-shadow: inset 3px 0 0 var(--accent);
}

/* Language toggle */
.lang-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.25rem;
    padding: 0.5rem 1rem;
    border-bottom: 1px solid #333;
}

.lang-btn {
    background: none;
    border: none;
    color: #666;
    font-family: inherit;
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    transition: background var(--transition-speed), color var(--transition-speed);
}

.lang-btn:hover {
    background: #2a2a2a;
    color: #fff;
}

.lang-btn.active {
    background: var(--accent);
    color: #fff;
}

.lang-sep {
    color: #444;
    font-size: 0.75rem;
}

/* Lesson completion indicators */
.lesson-list li a.completed {
    position: relative;
}

.lesson-list li a.completed::before {
    content: '';
    position: absolute;
    right: 1rem;
    top: 50%;
    transform: translateY(-50%);
    width: 8px;
    height: 8px;
    background: #4ec9b0;
    border-radius: 50%;
}

/* Certificate button */
.certificate-btn {
    margin: 1rem;
    padding: 0.75rem 1rem;
    background: var(--accent);
    color: #fff;
    border: none;
    border-radius: 8px;
    font-family: inherit;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: background var(--transition-speed), transform var(--transition-speed);
}

.certificate-btn:hover {
    background: var(--accent-hover);
    transform: translateY(-1px);
}

.certificate-btn:active {
    transform: translateY(0);
}

/* Modal styles */
.certificate-modal {
    position: fixed;
    inset: 0;
    z-index: 10000;
    display: flex;
    align-items: center;
    justify-content: center;
}

.modal-backdrop {
    position: absolute;
    inset: 0;
    background: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(4px);
}

.modal-content {
    position: relative;
    background: #fff;
    padding: 2.5rem;
    border-radius: 12px;
    max-width: 400px;
    width: 90%;
    text-align: center;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
}

.modal-content h2 {
    margin-bottom: 0.5rem;
    color: var(--text);
}

.modal-content p {
    margin-bottom: 1.5rem;
    color: var(--text-muted, #666);
}

.modal-close {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: #999;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.modal-close:hover {
    color: #333;
}

.name-input {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 2px solid var(--border);
    border-radius: 8px;
    font-family: inherit;
    font-size: 1rem;
    margin-bottom: 1rem;
    outline: none;
    transition: border-color var(--transition-speed);
}

.name-input:focus {
    border-color: var(--accent);
}

.generate-btn {
    width: 100%;
    padding: 0.75rem 1rem;
    background: var(--accent);
    color: #fff;
    border: none;
    border-radius: 8px;
    font-family: inherit;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background var(--transition-speed);
}

.generate-btn:hover {
    background: var(--accent-hover);
}

/* Certificate overlay */
.cert-overlay {
    position: fixed;
    inset: 0;
    z-index: 10000;
    background: rgba(0, 0, 0, 0.9);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 2rem;
    overflow-y: auto;
}

.certificate-wrapper {
    position: relative;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2rem;
}

#confetti {
    position: fixed;
    inset: 0;
    pointer-events: none;
    overflow: hidden;
}

.confetti-piece {
    position: absolute;
    top: -10px;
    width: 10px;
    height: 10px;
    opacity: 0;
    animation: confetti-fall 3s ease-out forwards;
}

@keyframes confetti-fall {
    0% {
        opacity: 1;
        transform: translateY(0) rotate(0deg);
    }
    100% {
        opacity: 0;
        transform: translateY(100vh) rotate(720deg);
    }
}

/* Certificate design */
.certificate {
    background: #fff;
    padding: 3rem 4rem;
    border: 3px solid var(--accent);
    border-radius: 4px;
    max-width: 700px;
    width: 100%;
    text-align: center;
    box-shadow: 0 0 0 8px rgba(108, 92, 231, 0.1);
}

.cert-header {
    margin-bottom: 2rem;
}

.cert-logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--accent);
    margin-bottom: 1rem;
}

.cert-title {
    font-size: 0.875rem;
    letter-spacing: 0.2em;
    text-transform: uppercase;
    color: #999;
    border-bottom: 1px solid #eee;
    padding-bottom: 1rem;
}

.cert-body {
    padding: 2rem 0;
}

.cert-presents,
.cert-completes {
    color: #666;
    margin-bottom: 0.5rem;
}

.cert-name {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text);
    margin: 1rem 0 1.5rem;
    border-bottom: 2px solid var(--accent);
    padding-bottom: 1rem;
    display: inline-block;
}

.cert-course {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--accent);
    margin: 0.5rem 0;
}

.cert-meta {
    color: #999;
    font-size: 0.875rem;
    margin-top: 1rem;
}

.cert-id {
    color: var(--accent);
    font-size: 0.875rem;
    font-weight: 600;
    margin-top: 0.5rem;
    letter-spacing: 0.1em;
}

.cert-footer {
    border-top: 1px solid #eee;
    padding-top: 1.5rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
}

.cert-marketing {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text);
    font-style: italic;
}

.cert-school {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text);
}

.cert-actions {
    display: flex;
    gap: 1rem;
}

.print-btn,
.close-btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 8px;
    font-family: inherit;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: background var(--transition-speed);
}

.print-btn {
    background: var(--accent);
    color: #fff;
}

.print-btn:hover {
    background: var(--accent-hover);
}

.close-btn {
    background: #eee;
    color: var(--text);
}

.close-btn:hover {
    background: #ddd;
}

/* Print styles - only print certificate */
@media print {
    body {
        background: #fff;
    }

    .container,
    .sidebar,
    #lesson-content,
    .cert-overlay .certificate-wrapper .cert-actions {
        display: none !important;
    }

    .cert-overlay {
        position: static;
        background: #fff;
        padding: 0;
    }

    .certificate-wrapper {
        padding: 0;
    }

    .certificate {
        box-shadow: none;
        border: 2px solid var(--accent);
        margin: 0;
        padding: 2rem;
    }

    #confetti {
        display: none;
    }
}

.lesson-list {
    flex: 1;
    overflow-y: auto;
    padding: 1rem 0;
}

.lesson-list ul {
    list-style: none;
}

.lesson-list li a {
    display: block;
    padding: var(--link-padding);
    color: var(--sidebar-text);
    text-decoration: none;
    font-size: var(--font-size-sm);
    transition: background var(--transition-speed), color var(--transition-speed);
    outline: none;
}

.lesson-list li a:hover {
    background: #2a2a2a;
    color: #fff;
}

.lesson-list li a:focus-visible {
    background: #2a2a2a;
    color: #fff;
    box-shadow: inset 3px 0 0 var(--accent);
}

.lesson-list li a.active {
    background: var(--accent);
    color: #fff;
}

.content {
    flex: 1;
    overflow-y: auto;
    padding: var(--content-padding);
    background: var(--bg);
}

#lesson-content {
    max-width: 800px;
    margin: 0 auto;
}

#lesson-content:focus {
    outline: none;
}

#lesson-content h1 {
    font-size: var(--font-size-h1);
    margin-bottom: 1.5rem;
    color: var(--text);
}

#lesson-content h2 {
    font-size: var(--font-size-h2);
    margin: 1.5rem 0 1rem;
    color: var(--text);
}

#lesson-content h3 {
    font-size: var(--font-size-h3);
    margin: 1.25rem 0 0.75rem;
    color: var(--text);
}

#lesson-content p {
    margin-bottom: 1rem;
}

#lesson-content code {
    font-family: 'JetBrains Mono', monospace;
    background: #2d2d2d;
    color: #f8f8f2;
    padding: 0.15rem 0.4rem;
    border-radius: 3px;
    font-size: 0.9em;
}

#lesson-content pre[class*="language-"],
#lesson-content pre[class*="language-"] code {
    font-family: 'JetBrains Mono', monospace;
    background: #1a1a1a;
    color: #d4d4d4;
    padding: 0;
    font-size: 0.9rem;
    line-height: 1.5;
    text-shadow: none;
}

#lesson-content pre[class*="language-"] {
    background: #1a1a1a;
    padding: 1rem;
    border-radius: 6px;
    overflow-x: auto;
    margin: 1rem 0;
}

#lesson-content code[class*="language-"] {
    display: block;
    padding: 0;
    background: none;
}

/* Prism Tomorrow Night token colors */
.token.comment,
.token.prolog,
.token.doctype,
.token.cdata {
    color: #6a9955;
}

.token.punctuation {
    color: #d4d4d4;
}

.token.property,
.token.tag,
.token.boolean,
.token.number,
.token.constant,
.token.symbol,
.token.deleted {
    color: #b5cea8;
}

.token.selector,
.token.attr-name,
.token.string,
.token.char,
.token.builtin,
.token.inserted {
    color: #ce9178;
}

.token.operator,
.token.entity,
.token.url,
.language-css .token.string,
.style .token.string {
    color: #d4d4d4;
}

.token.atrule,
.token.attr-value,
.token.keyword {
    color: #569cd6;
}

.token.function,
.token.class-name {
    color: #dcdcaa;
}

.token.regex,
.token.important,
.token.variable {
    color: #d16969;
}

.token.parameter {
    color: #9cdcfe;
}

.token.builtin {
    color: #4ec9b0;
}

#lesson-content ul, #lesson-content ol {
    margin: 1rem 0;
    padding-left: 1.5rem;
}

#lesson-content li {
    margin-bottom: 0.5rem;
}

#lesson-content blockquote {
    border-left: 3px solid var(--accent);
    padding-left: 1rem;
    margin: 1rem 0;
    color: #666;
}

.loading {
    color: #999;
    font-style: italic;
}

@media (prefers-reduced-motion: reduce) {
    .lesson-list li a,
    .skip-link {
        transition: none;
    }
}

@media (max-width: 1024px) {
    :root {
        --sidebar-width: 240px;
        --content-padding: 2rem;
    }
}

@media (max-width: 768px) {
    .container {
        flex-direction: column;
    }

    .sidebar {
        width: 100%;
        min-width: 100%;
        max-width: 100%;
        height: auto;
        max-height: 35vh;
    }

    .sidebar-header {
        padding: 1rem;
    }

    .sidebar-header h1 {
        font-size: 1rem;
    }

    .content {
        padding: 1.5rem;
    }

    :root {
        --font-size-h1: 1.5rem;
        --font-size-h2: 1.2rem;
    }
}

@media (max-width: 480px) {
    .content {
        padding: 1rem;
    }

    .lesson-list li a {
        padding: 0.6rem 1rem;
        font-size: 0.8rem;
    }

    #lesson-content pre {
        padding: 0.75rem;
        font-size: 0.85rem;
    }
}