/* ============================================================
   On-device AI tutor (Gemma 4 / WebGPU via transformers.js v4)
   Theme-aware: pulls colour vars from the page's :root rules.
   ============================================================ */

:root {
    --chat-fab-size: 56px;
    --chat-panel-width: 380px;
    --chat-panel-height: 560px;
}

.chat-fab {
    position: fixed;
    right: 20px;
    bottom: 20px;
    width: var(--chat-fab-size);
    height: var(--chat-fab-size);
    border-radius: 50%;
    background: var(--accent);
    color: var(--bg);
    border: 2px solid var(--gold);
    box-shadow: var(--shadow-lg);
    cursor: pointer;
    z-index: 90;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform 0.18s ease, background 0.18s ease;
    font-family: 'Segoe UI', Helvetica, Arial, sans-serif;
}
html[data-theme="dark"] .chat-fab { color: #0f1724; }
.chat-fab:hover { transform: translateY(-2px); background: var(--accent-hover); }
.chat-fab svg { width: 26px; height: 26px; }
.chat-fab .badge {
    position: absolute;
    top: -4px; right: -4px;
    background: var(--gold);
    color: #0f1724;
    font-size: 0.62rem;
    font-weight: 700;
    padding: 2px 6px;
    border-radius: 10px;
    letter-spacing: 0.4px;
}

/* Hide FAB while the panel is open (panel has its own close button) */
.chat-panel.open ~ .chat-fab,
body.chat-open .chat-fab { display: none; }

/* --- Slide-out panel --- */
.chat-panel {
    position: fixed;
    right: 20px;
    bottom: 20px;
    width: var(--chat-panel-width);
    max-width: calc(100vw - 32px);
    height: var(--chat-panel-height);
    max-height: calc(100vh - 80px);
    background: var(--card-bg);
    color: var(--text);
    border: 1px solid var(--border);
    border-radius: 14px;
    box-shadow: var(--shadow-lg);
    transform: translateY(20px) scale(0.96);
    opacity: 0;
    pointer-events: none;
    transition: transform 0.2s ease, opacity 0.2s ease;
    z-index: 95;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    font-family: 'Segoe UI', Helvetica, Arial, sans-serif;
}
.chat-panel.open {
    transform: translateY(0) scale(1);
    opacity: 1;
    pointer-events: auto;
}

.chat-header {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 14px;
    background: var(--accent);
    color: var(--bg);
    border-bottom: 1px solid var(--border);
}
html[data-theme="dark"] .chat-header { color: #0f1724; }
.chat-header .chat-title {
    flex: 1;
    font-weight: 700;
    font-size: 0.95rem;
    line-height: 1.2;
    display: flex;
    flex-direction: column;
}
.chat-header .chat-subtitle {
    font-size: 0.7rem;
    font-weight: 400;
    opacity: 0.85;
    margin-top: 1px;
}
.chat-header button {
    background: rgba(255,255,255,0.15);
    border: none;
    color: inherit;
    cursor: pointer;
    border-radius: 6px;
    padding: 4px 8px;
    font-size: 0.85rem;
    line-height: 1;
    transition: background 0.15s;
}
.chat-header button:hover { background: rgba(255,255,255,0.28); }

.chat-body {
    flex: 1;
    overflow-y: auto;
    padding: 14px;
    display: flex;
    flex-direction: column;
    gap: 10px;
    background: var(--bg);
    scrollbar-width: thin;
    scrollbar-color: var(--scrollbar-thumb) var(--scrollbar-track);
}
.chat-body::-webkit-scrollbar { width: 8px; }
.chat-body::-webkit-scrollbar-track { background: var(--scrollbar-track); }
.chat-body::-webkit-scrollbar-thumb {
    background: var(--scrollbar-thumb);
    border-radius: 6px;
    border: 2px solid var(--scrollbar-track);
}

.chat-msg {
    max-width: 85%;
    padding: 9px 12px;
    border-radius: 12px;
    font-size: 0.88rem;
    line-height: 1.45;
    white-space: pre-wrap;
    word-break: break-word;
}
.chat-msg.user {
    align-self: flex-end;
    background: var(--accent);
    color: var(--bg);
    border-bottom-right-radius: 4px;
}
html[data-theme="dark"] .chat-msg.user { color: #0f1724; }
.chat-msg.bot {
    align-self: flex-start;
    background: var(--code-bg);
    color: var(--text);
    border: 1px solid var(--border);
    border-bottom-left-radius: 4px;
}
.chat-msg.bot.markdown-rendered {
    white-space: normal;
    overflow-wrap: anywhere;
}
.chat-msg.bot.markdown-rendered > :first-child { margin-top: 0; }
.chat-msg.bot.markdown-rendered > :last-child { margin-bottom: 0; }
.chat-msg.bot.markdown-rendered p,
.chat-msg.bot.markdown-rendered ul,
.chat-msg.bot.markdown-rendered ol,
.chat-msg.bot.markdown-rendered pre,
.chat-msg.bot.markdown-rendered blockquote,
.chat-msg.bot.markdown-rendered hr,
.chat-msg.bot.markdown-rendered h1,
.chat-msg.bot.markdown-rendered h2,
.chat-msg.bot.markdown-rendered h3,
.chat-msg.bot.markdown-rendered h4,
.chat-msg.bot.markdown-rendered h5,
.chat-msg.bot.markdown-rendered h6 {
    margin: 0.55rem 0;
}
.chat-msg.bot.markdown-rendered ul,
.chat-msg.bot.markdown-rendered ol {
    padding-left: 1.25rem;
}
.chat-msg.bot.markdown-rendered li + li {
    margin-top: 0.25rem;
}
.chat-msg.bot.markdown-rendered a {
    color: var(--accent);
}
.chat-msg.bot.markdown-rendered a:hover {
    color: var(--accent-hover);
}
.chat-msg.bot.markdown-rendered code {
    font-family: 'SF Mono', 'Fira Code', 'Consolas', monospace;
    font-size: 0.84em;
    background: rgba(255, 255, 255, 0.06);
    border: 1px solid var(--border);
    border-radius: 5px;
    padding: 0.08rem 0.34rem;
}
.chat-msg.bot.markdown-rendered .chat-code-block {
    margin: 0.65rem 0;
    padding: 0.8rem 0.95rem;
    background: rgba(15, 23, 36, 0.08);
    border: 1px solid var(--border);
    border-radius: 10px;
    overflow-x: auto;
}
.chat-msg.bot.markdown-rendered .chat-code-block code {
    display: block;
    padding: 0;
    border: none;
    border-radius: 0;
    background: transparent;
    white-space: pre;
}
.chat-msg.bot.markdown-rendered blockquote {
    margin-left: 0;
    margin-right: 0;
    padding: 0.75rem 0.9rem;
    border-left: 3px solid var(--gold);
    background: rgba(255, 215, 0, 0.08);
    border-radius: 0 10px 10px 0;
}
.chat-msg.bot.markdown-rendered hr {
    border: 0;
    border-top: 1px solid var(--border);
}

.chat-mermaid-block {
    position: relative;
    margin: 0.75rem 0;
    padding: 0.7rem;
    border: 1px solid var(--border);
    border-radius: 12px;
    background: linear-gradient(180deg, rgba(255, 255, 255, 0.06), rgba(255, 255, 255, 0.02));
}
.chat-mermaid-toolbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 0.6rem;
    margin-bottom: 0.7rem;
}
.chat-mermaid-toggle {
    display: inline-flex;
    align-items: center;
    gap: 0.22rem;
    padding: 0.2rem;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 999px;
}
.chat-mermaid-toggle button {
    border: none;
    background: transparent;
    color: var(--muted);
    border-radius: 999px;
    padding: 0.28rem 0.72rem;
    font-size: 0.76rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.15s ease, color 0.15s ease, transform 0.15s ease;
}
.chat-mermaid-toggle button:hover {
    color: var(--text);
}
.chat-mermaid-toggle button.active {
    background: var(--accent);
    color: var(--bg);
}
html[data-theme="dark"] .chat-mermaid-toggle button.active {
    color: #0f1724;
}
.chat-mermaid-selection-status {
    min-height: 1.1rem;
    font-size: 0.72rem;
    color: var(--muted);
    text-align: right;
}
.chat-mermaid-selection-status.has-selection {
    color: var(--accent);
}
.chat-mermaid-diagram,
.chat-mermaid-source {
    margin: 0;
    border: 1px solid rgba(255, 255, 255, 0.08);
    border-radius: 10px;
    background: rgba(15, 23, 36, 0.12);
}
.chat-mermaid-diagram {
    padding: 0.85rem;
    overflow-x: auto;
    text-align: center;
    cursor: cell;
}
.chat-mermaid-diagram svg {
    max-width: 100%;
    height: auto;
}
.chat-mermaid-source {
    display: none;
    overflow: auto;
    padding: 0.85rem 0.9rem;
}
.chat-mermaid-block[data-view="source"] .chat-mermaid-diagram {
    display: none;
}
.chat-mermaid-block[data-view="source"] .chat-mermaid-source {
    display: block;
}
.chat-mermaid-source code {
    display: block;
    font-family: 'SF Mono', 'Fira Code', 'Consolas', monospace;
    font-size: 0.79rem;
    line-height: 1.45;
}
.chat-mermaid-source-line {
    position: relative;
    display: block;
    min-height: 1.45em;
    padding-left: 2.8rem;
    white-space: pre-wrap;
    word-break: break-word;
}
.chat-mermaid-source-line::before {
    content: attr(data-line-number);
    position: absolute;
    left: 0;
    width: 2rem;
    text-align: right;
    color: var(--muted);
    user-select: none;
}
.chat-mermaid-diagram:focus,
.chat-mermaid-source:focus {
    outline: 1px solid var(--accent);
    outline-offset: 2px;
}
.chat-mermaid-selection-proxy {
    position: absolute;
    left: -9999px;
    width: 1px;
    height: 1px;
    opacity: 0;
    pointer-events: none;
}
.chat-msg.system {
    align-self: center;
    background: transparent;
    color: var(--muted);
    font-size: 0.78rem;
    font-style: italic;
    max-width: 100%;
    text-align: center;
}
.chat-msg.error {
    align-self: stretch;
    background: rgba(220, 50, 50, 0.12);
    color: #c43232;
    border: 1px solid rgba(220, 50, 50, 0.4);
    font-size: 0.82rem;
}

/* --- Intro / capability screen --- */
.chat-intro {
    flex: 1;
    overflow-y: auto;
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 14px;
    background: var(--bg);
}
.chat-intro h3 {
    margin: 0;
    font-size: 1rem;
    color: var(--heading);
}
.chat-intro p {
    margin: 0;
    font-size: 0.85rem;
    line-height: 1.55;
    color: var(--text);
}
.chat-intro ul {
    margin: 0;
    padding-left: 18px;
    font-size: 0.82rem;
    color: var(--muted);
}
.chat-intro li { margin-bottom: 4px; }
.chat-intro .muted {
    font-size: 0.75rem;
    color: var(--muted);
}

.chat-load-btn {
    background: var(--accent);
    color: var(--bg);
    border: 1px solid var(--gold);
    border-radius: 8px;
    padding: 10px 14px;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.15s, transform 0.1s;
    font-family: inherit;
}
html[data-theme="dark"] .chat-load-btn { color: #0f1724; }
.chat-load-btn:hover { background: var(--accent-hover); }
.chat-load-btn:active { transform: scale(0.98); }
.chat-load-btn:disabled {
    background: var(--border);
    color: var(--muted);
    cursor: not-allowed;
    border-color: var(--border);
}
html[data-theme="dark"] .chat-load-btn:disabled { color: var(--muted); }

.chat-progress {
    display: flex;
    flex-direction: column;
    gap: 6px;
    font-size: 0.8rem;
    color: var(--muted);
}
.chat-progress-bar {
    height: 8px;
    background: var(--code-bg);
    border-radius: 4px;
    overflow: hidden;
    border: 1px solid var(--border);
}
.chat-progress-fill {
    height: 100%;
    background: var(--gold);
    width: 0%;
    transition: width 0.2s ease;
}
.chat-progress-label {
    display: flex;
    justify-content: space-between;
    font-variant-numeric: tabular-nums;
}

/* --- Composer --- */
.chat-composer {
    display: flex;
    gap: 8px;
    padding: 10px 12px;
    border-top: 1px solid var(--border);
    background: var(--card-bg);
}
.chat-composer textarea {
    flex: 1;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 8px 10px;
    font-size: 0.88rem;
    font-family: inherit;
    background: var(--bg);
    color: var(--text);
    resize: none;
    max-height: 120px;
    min-height: 36px;
    line-height: 1.4;
    outline: none;
    transition: border-color 0.15s;
}
.chat-composer textarea:focus { border-color: var(--accent); }
.chat-composer button {
    background: var(--accent);
    color: var(--bg);
    border: none;
    border-radius: 8px;
    padding: 0 14px;
    cursor: pointer;
    font-weight: 600;
    font-family: inherit;
    transition: background 0.15s;
    display: flex;
    align-items: center;
    justify-content: center;
}
html[data-theme="dark"] .chat-composer button { color: #0f1724; }
.chat-composer button:hover { background: var(--accent-hover); }
.chat-composer button:disabled {
    background: var(--border);
    color: var(--muted);
    cursor: not-allowed;
}
.chat-composer button svg { width: 18px; height: 18px; }

/* --- Cross-lesson index controls --- */
.chat-index-options {
    margin: 14px 0 4px;
    padding: 12px;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: color-mix(in srgb, var(--card-bg) 92%, var(--accent) 8%);
}
.chat-index-label {
    margin: 0 0 4px;
    font-weight: 600;
    font-size: 0.92rem;
}
.chat-index-help {
    margin: 0 0 10px;
    font-size: 0.82rem;
    line-height: 1.4;
    color: var(--muted);
}
.chat-index-checkbox {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 4px 0;
    font-size: 0.88rem;
    cursor: pointer;
    user-select: none;
}
.chat-index-checkbox input[type="checkbox"] {
    cursor: pointer;
    accent-color: var(--accent);
}
.chat-index-checkbox input[type="checkbox"]:disabled {
    cursor: default;
}
.chat-index-checkbox input[type="checkbox"]:disabled + span {
    color: var(--muted);
}

/* --- Status bar with index chip --- */
.chat-status-bar {
    display: flex;
    justify-content: flex-end;
    align-items: center;
    padding: 6px 12px;
    border-bottom: 1px solid var(--border);
    background: color-mix(in srgb, var(--card-bg) 96%, var(--accent) 4%);
    flex-shrink: 0;
}
.chat-index-chip {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    padding: 3px 10px;
    border-radius: 999px;
    border: 1px solid var(--border);
    background: var(--card-bg);
    color: var(--text);
    font-size: 0.74rem;
    font-weight: 500;
    cursor: pointer;
    font-family: inherit;
    transition: background 0.15s ease, border-color 0.15s ease;
}
.chat-index-chip:hover:not(:disabled) {
    background: color-mix(in srgb, var(--accent) 12%, var(--card-bg) 88%);
    border-color: var(--accent);
}
.chat-index-chip:disabled { cursor: default; }
.chat-index-chip.ready {
    background: color-mix(in srgb, #2e7d32 18%, var(--card-bg) 82%);
    border-color: #2e7d32;
    color: #1b5e20;
}
html[data-theme="dark"] .chat-index-chip.ready {
    background: color-mix(in srgb, #66bb6a 22%, var(--card-bg) 78%);
    color: #a5d6a7;
}
.chat-index-chip.indexing {
    background: color-mix(in srgb, var(--gold) 20%, var(--card-bg) 80%);
    border-color: var(--gold);
}
.chat-index-chip.error {
    background: color-mix(in srgb, #c62828 18%, var(--card-bg) 82%);
    border-color: #c62828;
    color: #b71c1c;
}
html[data-theme="dark"] .chat-index-chip.error {
    color: #ef9a9a;
}

/* --- Mobile --- */
@media (max-width: 640px) {
    .chat-panel {
        right: 10px;
        bottom: 10px;
        left: 10px;
        width: auto;
        max-width: none;
        height: 70vh;
    }
    .chat-fab { right: 14px; bottom: 14px; }
}