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

:root {
    --bg-primary: #0d1117;
    --bg-secondary: #161b22;
    --bg-tertiary: #21262d;
    --text-primary: #e6edf3;
    --text-secondary: #8b949e;
    --border-color: #30363d;
    --accent: #58a6ff;
    --accent-hover: #79b8ff;
    --success: #3fb950;
    --warning: #d29922;
    --error: #f85149;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
}

.layout {
    display: flex;
    min-height: 100vh;
}

/* Sidebar */
.sidebar {
    width: 280px;
    background-color: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    padding: 1.5rem;
    position: fixed;
    height: 100vh;
    overflow-y: auto;
}

.logo {
    margin-bottom: 2rem;
}

.logo a {
    color: var(--text-primary);
    text-decoration: none;
    font-size: 1.25rem;
    font-weight: 600;
}

.nav-section h3 {
    color: var(--text-secondary);
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 1rem;
}

.phase-group {
    margin-bottom: 1.5rem;
}

.phase-group h4 {
    color: var(--text-primary);
    font-size: 0.875rem;
    margin-bottom: 0.5rem;
    padding-left: 0.5rem;
}

.phase-group ul {
    list-style: none;
}

.phase-group li {
    margin-bottom: 0.25rem;
}

.phase-group li a {
    display: block;
    padding: 0.5rem;
    color: var(--text-secondary);
    text-decoration: none;
    border-radius: 6px;
    font-size: 0.875rem;
    transition: all 0.15s ease;
}

.phase-group li a:hover {
    background-color: var(--bg-tertiary);
    color: var(--text-primary);
}

.phase-group li.active a {
    background-color: var(--accent);
    color: white;
}

/* Main content */
.content {
    flex: 1;
    margin-left: 280px;
    padding: 2rem;
    max-width: calc(100vw - 280px);
}

/* Home page */
.home h1 {
    margin-bottom: 2rem;
}

.intro-card {
    margin-bottom: 2rem;
}

.roadmap-overview {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 1.5rem;
}

.roadmap-overview h2 {
    grid-column: 1 / -1;
    margin-bottom: 0.5rem;
}

.phase-card {
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1.5rem;
}

.phase-card h3 {
    margin-bottom: 1rem;
    color: var(--accent);
}

.phase-card ul {
    list-style: none;
}

.phase-card li {
    margin-bottom: 0.5rem;
}

.phase-card a {
    color: var(--text-secondary);
    text-decoration: none;
}

.phase-card a:hover {
    color: var(--accent);
}

.empty-state {
    color: var(--text-secondary);
    font-style: italic;
}

/* Section page */
.section-header {
    margin-bottom: 2rem;
}

.phase-badge {
    display: inline-block;
    background-color: var(--accent);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    margin-bottom: 0.5rem;
}

.section-grid {
    display: grid;
    grid-template-columns: 1fr 400px;
    gap: 2rem;
}

@media (max-width: 1200px) {
    .section-grid {
        grid-template-columns: 1fr;
    }
}

.section-main {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

/* Cards */
.card {
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1.5rem;
}

.card h2 {
    font-size: 1rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--border-color);
}

/* Tasks */
.task-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.task-item {
    padding: 0.75rem;
    background-color: var(--bg-tertiary);
    border-radius: 6px;
}

.task-checkbox {
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
    cursor: pointer;
}

.task-checkbox input[type="checkbox"] {
    width: 18px;
    height: 18px;
    margin-top: 0.125rem;
    accent-color: var(--success);
}

.task-checkbox input[type="checkbox"]:checked + .task-description {
    text-decoration: line-through;
    color: var(--text-secondary);
}

.task-hint {
    margin-top: 0.5rem;
    margin-left: 1.75rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
    font-style: italic;
}

.task-guide-actions {
    margin-top: 0.75rem;
    margin-left: 1.75rem;
}

.btn-guide {
    background-color: transparent;
    border: 1px solid var(--border-color);
    color: var(--accent);
    padding: 0.35rem 0.75rem;
    font-size: 0.8rem;
}

.btn-guide:hover {
    background-color: var(--bg-primary);
    border-color: var(--accent);
}

.btn-guide:disabled {
    opacity: 0.6;
    cursor: progress;
}

.task-guide {
    margin-top: 0.75rem;
    margin-left: 1.75rem;
    padding: 0.9rem 1rem;
    background-color: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-left: 3px solid var(--accent);
    border-radius: 6px;
    font-size: 0.875rem;
    color: var(--text-primary);
    white-space: pre-wrap;
    word-wrap: break-word;
}

.task-guide.hidden {
    display: none;
}

/* Chat */
.chat-card {
    display: flex;
    flex-direction: column;
    height: calc(100vh - 8rem);
    position: sticky;
    top: 2rem;
}

.chat-messages {
    flex: 1;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    padding: 1rem 0;
}

.message {
    padding: 0.75rem 1rem;
    border-radius: 8px;
    max-width: 90%;
}

.message.user {
    background-color: var(--accent);
    color: white;
    align-self: flex-end;
}

.message.assistant {
    background-color: var(--bg-tertiary);
    align-self: flex-start;
}

.message-content {
    white-space: pre-wrap;
    word-wrap: break-word;
}

.empty-chat {
    color: var(--text-secondary);
    text-align: center;
    padding: 2rem;
}

.chat-input {
    display: flex;
    gap: 0.5rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border-color);
    margin-top: auto;
}

.chat-input textarea {
    flex: 1;
    background-color: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    padding: 0.75rem;
    color: var(--text-primary);
    font-family: inherit;
    font-size: 0.875rem;
    resize: none;
}

.chat-input textarea:focus {
    outline: none;
    border-color: var(--accent);
}

/* Quiz */
.quiz-question {
    margin: 1rem 0;
    padding: 1rem;
    background-color: var(--bg-tertiary);
    border-radius: 6px;
}

.quiz-question.hidden {
    display: none;
}

#quiz-answer-form {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

#quiz-answer-form.hidden {
    display: none;
}

#quiz-answer {
    background-color: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    padding: 0.75rem;
    color: var(--text-primary);
    font-family: inherit;
    min-height: 100px;
    resize: vertical;
}

/* Buttons */
.btn {
    background-color: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.5rem 1rem;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.875rem;
    font-weight: 500;
    transition: all 0.15s ease;
}

.btn:hover {
    background-color: var(--border-color);
}

.btn-primary {
    background-color: var(--accent);
    border-color: var(--accent);
    color: white;
}

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

/* Error page */
.error-page {
    text-align: center;
    padding: 4rem 2rem;
}

.error-page h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.error-page p {
    color: var(--text-secondary);
    margin-bottom: 2rem;
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: var(--bg-secondary);
}

::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}