:root {
    /* Dark theme (default) */
    --bg-color: #0F172A;
    --surface-color: #1E293B;
    --surface-hover: #334155;
    --accent-color: #3B82F6;
    --accent-hover: #2563EB;
    --text-primary: #E2E8F0;
    --text-secondary: #94A3B8;
    --success: #22C55E;
    --warning: #EAB308;
    --danger: #EF4444;
    --border-color: #334155;
    --shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -4px rgba(0, 0, 0, 0.4);
    --bubble-radius: 18px;
    --font-family: 'Inter', system-ui, -apple-system, sans-serif;
    --header-bg: rgba(15, 23, 42, 0.75);
    --code-bg: rgba(0,0,0,0.4);
    --token-info-bg: rgba(59, 130, 246, 0.1);
    --system-msg-bg: rgba(51, 65, 85, 0.3);
}

/* ---- Light Mode Overrides ---- */
body.light-mode {
    --bg-color: #F1F5F9;
    --surface-color: #FFFFFF;
    --surface-hover: #E2E8F0;
    --accent-color: #2563EB;
    --accent-hover: #1D4ED8;
    --text-primary: #0F172A;
    --text-secondary: #64748B;
    --border-color: #CBD5E1;
    --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.07), 0 2px 4px -2px rgb(0 0 0 / 0.05);
    --header-bg: rgba(241, 245, 249, 0.85);
    --code-bg: rgba(15, 23, 42, 0.07);
    --token-info-bg: rgba(203, 213, 225, 0.35);
    --system-msg-bg: rgba(148, 163, 184, 0.15);
}

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

/* Smooth theme transitions */
body, body * {
    transition: background-color 0.25s ease, color 0.25s ease,
                border-color 0.25s ease, box-shadow 0.25s ease;
}

body {
    font-family: var(--font-family);
    background-color: var(--bg-color);
    color: var(--text-primary);
    height: 100vh;
    height: 100dvh;
    overflow: hidden;
    line-height: 1.5;
}

.app-container {
    display: flex;
    height: 100vh;
    height: 100dvh;
    width: 100%;
    overflow: hidden;
}

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

/* --- Chat Area --- */
.chat-area {
    flex: 1;
    display: flex;
    flex-direction: column;
    background-color: var(--bg-color);
    position: relative;
    border-right: 1px solid var(--border-color);
}

.chat-header {
    padding: 0.75rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    background-color: var(--header-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    z-index: 50;
    height: 64px;
}

.header-left {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.chat-header h1 {
    font-size: 1.15rem;
    font-weight: 800;
    color: var(--text-primary);
    letter-spacing: -0.03em;
    background: linear-gradient(135deg, var(--text-primary) 0%, var(--accent-color) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.status-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
}

.status-dot.online {
    background-color: var(--success);
    box-shadow: 0 0 8px var(--success);
}

/* --- Chat Window --- */
.chat-window {
    flex: 1;
    overflow-y: auto;
    padding: 2rem;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    scroll-behavior: smooth;
}

.chat-window::-webkit-scrollbar {
    width: 6px;
}

.chat-window::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 10px;
}

.welcome-message {
    text-align: center;
    margin: auto;
    max-width: 480px;
    padding: 3rem 2rem;
    background-color: var(--surface-color);
    border-radius: 24px;
    border: 1px solid var(--border-color);
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.2);
    background: linear-gradient(135deg, var(--surface-color) 0%, rgba(30, 41, 59, 0.5) 100%);
}

.welcome-message h3 {
    margin-bottom: 0.5rem;
}

.welcome-message p {
    color: var(--text-secondary);
}

/* --- Messages --- */
.message {
    max-width: 80%;
    position: relative;
    animation: fadeIn 0.3s ease-out;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.message-header {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 0.25rem;
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.message-content {
    padding: 1rem;
    border-radius: var(--bubble-radius);
    box-shadow: var(--shadow);
    position: relative;
    font-size: 0.95rem;
}

.message-content > * + * {
    margin-top: 0.75rem;
}

.message-content p {
    word-break: break-word;
}

.message-content ul, .message-content ol {
    padding-left: 1.5rem;
}

.message-content li {
    margin-bottom: 0.25rem;
}

.message-content h1, .message-content h2, .message-content h3 {
    margin-top: 1rem;
    margin-bottom: 0.5rem;
    font-size: 1.1rem;
}

.message-content strong {
    color: inherit;
    font-weight: 700;
}

.message-content code {
    background-color: var(--code-bg);
    padding: 0.2rem 0.4rem;
    border-radius: 4px;
    font-family: monospace;
    font-size: 0.85em;
}

.message.user {
    align-self: flex-end;
}

.message.user .message-content {
    background-color: var(--accent-color);
    color: white;
    border-bottom-right-radius: 4px;
}

.message.assistant {
    align-self: flex-start;
}

.message.assistant .message-content {
    background-color: var(--surface-color);
    color: var(--text-primary);
    border-bottom-left-radius: 4px;
    border: 1px solid var(--border-color);
}

.message.system {
    align-self: center;
    max-width: 90%;
}

.message.system .message-content {
    background-color: var(--system-msg-bg);
    border: 1px dashed var(--border-color);
    font-style: italic;
    font-size: 0.9rem;
    text-align: center;
}

.message.pinned .message-content {
    border: 2px solid var(--warning);
}

.message-actions {
    position: absolute;
    top: 0;
    right: -40px;
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
    opacity: 0;
    transition: opacity 0.2s;
}

.message.user .message-actions {
    right: auto;
    left: -40px;
}

.message:hover .message-actions {
    opacity: 1;
}

.action-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 4px;
    border-radius: 4px;
    transition: background 0.2s, color 0.2s;
}

.action-btn:hover {
    background-color: var(--surface-hover);
    color: var(--text-primary);
}

.action-btn.pin-btn.active {
    color: var(--warning);
}

.action-btn.delete-btn:hover {
    color: var(--danger);
}

/* --- Input Area --- */
.input-container {
    padding: 0.75rem 2rem;
    background-color: var(--bg-color);
    border-top: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.lock-message {
    background-color: rgba(239, 68, 68, 0.1);
    border: 1px solid var(--danger);
    color: var(--danger);
    padding: 0.75rem 1rem;
    border-radius: 8px;
    font-size: 0.85rem;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    max-width: 800px;
    margin: 0 auto;
    width: 100%;
    animation: slideUp 0.3s ease-out;
}

@keyframes slideUp {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.input-locked {
    opacity: 0.5;
    pointer-events: none;
    filter: grayscale(1);
    cursor: not-allowed;
}

.input-wrapper {
    max-width: 850px;
    margin: 0 auto;
    width: 100%;
    background-color: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    display: flex;
    align-items: flex-end;
    padding: 0.65rem 1.25rem;
    gap: 0.75rem;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: var(--shadow);
}

.input-wrapper:focus-within {
    border-color: var(--accent-color);
    box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.15), var(--shadow);
    transform: translateY(-2px);
}

#user-input {
    flex: 1;
    background: none;
    border: none;
    color: var(--text-primary);
    font-family: inherit;
    font-size: 1rem;
    resize: none;
    outline: none;
    max-height: 200px;
    padding-top: 0.25rem;
}

#send-btn {
    background-color: var(--accent-color);
    color: white;
    border: none;
    border-radius: 8px;
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: background 0.2s, transform 0.1s;
}

#send-btn:hover {
    background-color: var(--accent-hover);
}

#send-btn:active {
    transform: scale(0.95);
}

#send-btn:disabled {
    background-color: var(--border-color);
    cursor: not-allowed;
}

.message.assistant.typing .message-content {
    background-color: var(--surface-hover);
    border-style: dashed;
    display: inline-block;
    min-width: 60px;
}

.status-thinking {
    font-size: 0.7rem;
    color: var(--accent-color);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* --- Typing Dots Animation --- */
.typing-dots {
    display: flex;
    gap: 4px;
    padding: 0.25rem 0;
}

.typing-dots span {
    width: 6px;
    height: 6px;
    background-color: var(--text-secondary);
    border-radius: 50%;
    animation: typing 1.4s infinite ease-in-out;
}

.typing-dots span:nth-child(1) { animation-delay: 0s; }
.typing-dots span:nth-child(2) { animation-delay: 0.2s; }
.typing-dots span:nth-child(3) { animation-delay: 0.4s; }

@keyframes typing {
    0%, 60%, 100% { transform: translateY(0); opacity: 0.4; }
    30% { transform: translateY(-4px); opacity: 1; }
}

/* --- Sidebar --- */
.sidebar {
    width: 320px;
    background-color: var(--surface-color);
    padding: 2rem;
    display: flex;
    flex-direction: column;
    gap: 2rem;
    border-left: 1px solid var(--border-color);
    overflow-y: auto;
}

@media (max-width: 768px) {
    .sidebar {
        position: fixed;
        top: 0;
        left: -100%;
        width: 85%;
        max-width: 320px;
        height: 100%;
        z-index: 1000;
        transition: left 0.3s cubic-bezier(0.4, 0, 0.2, 1);
        border-left: none;
        border-right: 1px solid var(--border-color);
        box-shadow: 20px 0 50px rgba(0,0,0,0.5);
    }

    .sidebar.open {
        left: 0;
    }

    .chat-area {
        height: 100%;
        max-height: 100%;
        border-right: none;
    }

    .input-container {
        padding: 0.75rem 1rem;
    }
}

.panel h2 {
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-secondary);
    margin-bottom: 1.25rem;
}

/* --- Token Panel --- */
.token-stats {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.token-count {
    display: flex;
    align-items: baseline;
    gap: 0.5rem;
}

#current-tokens {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-primary);
}

.tokens-max {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.progress-container {
    height: 8px;
    background-color: var(--bg-color);
    border-radius: 4px;
    overflow: hidden;
}

.progress-bar {
    height: 100%;
    width: 0%;
    background-color: var(--success);
    transition: width 0.5s cubic-bezier(0.4, 0, 0.2, 1), background-color 0.3s;
}

.percentage-label {
    text-align: right;
    font-size: 0.875rem;
    font-weight: 500;
}

.token-info {
    margin-top: 1rem;
    font-size: 0.75rem;
    color: var(--text-secondary);
    padding: 0.75rem;
    background-color: var(--token-info-bg);
    border-radius: 8px;
}

/* --- Controls Panel --- */
.control-buttons {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem;
    border-radius: 8px;
    font-weight: 500;
    font-size: 0.875rem;
    cursor: pointer;
    transition: all 0.2s;
    border: 1px solid transparent;
    font-family: inherit;
}

.btn-secondary {
    background-color: var(--bg-color);
    color: var(--text-primary);
    border-color: var(--border-color);
}

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

.btn-danger {
    background-color: rgba(239, 68, 68, 0.1);
    color: var(--danger);
    border-color: rgba(239, 68, 68, 0.2);
}

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

.toggle-container {
    margin-top: 1.5rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.toggle-info h3 {
    font-size: 0.875rem;
    margin-bottom: 0.25rem;
}

.toggle-info p {
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.status-message {
    margin-top: 1rem;
    font-size: 0.875rem;
    text-align: center;
    min-height: 1.25rem;
}

/* --- Switch UI --- */
.switch {
    position: relative;
    display: inline-block;
    width: 44px;
    height: 24px;
}

.switch input { opacity: 0; width: 0; height: 0; }

.slider {
    position: absolute;
    cursor: pointer;
    top: 0; left: 0; right: 0; bottom: 0;
    background-color: var(--bg-color);
    transition: .4s;
    border: 1px solid var(--border-color);
}

.slider:before {
    position: absolute;
    content: "";
    height: 16px; width: 16px;
    left: 3px; bottom: 3px;
    background-color: var(--text-secondary);
    transition: .4s;
}

input:checked + .slider {
    background-color: var(--accent-color);
    border-color: var(--accent-color);
}

input:checked + .slider:before {
    transform: translateX(20px);
    background-color: white;
}

.slider.round { border-radius: 24px; }
.slider.round:before { border-radius: 50%; }

/* --- Mobile Only Elements --- */
.mobile-only {
    display: none !important;
}

.mobile-only-btn {
    display: none;
    background: none;
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    padding: 8px;
    border-radius: 8px;
    background-color: var(--surface-color);
    border: 1px solid var(--border-color);
}

.desktop-only {
    display: inline;
}

@media (max-width: 768px) {
    .mobile-only {
        display: flex !important;
    }
    
    .mobile-only-btn {
        display: flex;
    }
    
    .desktop-only {
        display: none !important;
    }
    
    .chat-window {
        padding: 1rem;
    }
    
    .message {
        max-width: 90%;
    }
}

.sidebar-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
}

.sidebar-header h2 {
    font-size: 1rem;
    font-weight: 700;
    margin: 0;
}

.close-btn {
    background: var(--surface-hover);
    border: none;
    color: var(--text-primary);
    width: 32px;
    height: 32px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
}

/* --- Compact Token Bar --- */
.compact-token-bar {
    flex: 1;
    max-width: 120px;
    height: 24px;
    background-color: var(--surface-color);
    border-radius: 12px;
    position: relative;
    overflow: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--border-color);
    margin: 0 1rem;
}

.compact-progress {
    position: absolute;
    left: 0;
    top: 0;
    height: 100%;
    width: 0%;
    background-color: var(--success);
    opacity: 0.3;
    transition: width 0.5s ease;
}

#compact-percentage {
    position: relative;
    font-size: 0.7rem;
    font-weight: 700;
    color: var(--text-primary);
    z-index: 1;
}

.sidebar-footer {
    margin-top: auto;
    font-size: 0.75rem;
    color: var(--text-secondary);
    text-align: center;
    padding-top: 2rem;
}

/* --- Dark Mode Toggle Button --- */
#theme-toggle {
    background: none;
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    cursor: pointer;
    padding: 6px 10px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    gap: 6px;
    font-size: 0.8rem;
    font-family: inherit;
    font-weight: 500;
    transition: all 0.2s;
    line-height: 1;
}

#theme-toggle:hover {
    background-color: var(--surface-hover);
    color: var(--text-primary);
    border-color: var(--accent-color);
}

#theme-toggle .theme-icon {
    font-size: 1rem;
    line-height: 1;
}

/* Prevent transition flicker on icons */
.theme-icon {
    transition: transform 0.3s ease;
}


#theme-toggle:hover .theme-icon {
    transform: rotate(20deg);
}

/* --- Attach Button (in input bar) --- */
.attach-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 6px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    transition: background 0.2s, color 0.2s;
}

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

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

.btn-primary:hover:not(:disabled) {
    background-color: var(--accent-hover);
}

.btn-primary:disabled {
    opacity: 0.45;
    cursor: not-allowed;
}

/* --- Upload Modal Overlay --- */
.modal-overlay {
    position: fixed;
    inset: 0;
    z-index: 100;
    background-color: rgba(0, 0, 0, 0.55);
    backdrop-filter: blur(4px);
    display: flex;
    align-items: center;
    justify-content: center;
    animation: fadeIn 0.2s ease-out;
}

.modal-card {
    background-color: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 1.75rem;
    width: 100%;
    max-width: 480px;
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.4);
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
    animation: slideUp 0.25s ease-out;
}

@keyframes slideUp {
    from { opacity: 0; transform: translateY(20px); }
    to   { opacity: 1; transform: translateY(0); }
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.modal-title {
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--text-primary);
}

.modal-close {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 4px;
    border-radius: 6px;
    display: flex;
    align-items: center;
    transition: background 0.2s, color 0.2s;
}

.modal-close:hover {
    background-color: var(--surface-hover);
    color: var(--text-primary);
}

/* --- Drop Zone --- */
.drop-zone {
    border: 2px dashed var(--border-color);
    border-radius: 12px;
    padding: 1.75rem 1rem;
    text-align: center;
    cursor: pointer;
    transition: border-color 0.2s, background-color 0.2s;
    position: relative;
}

.drop-zone:hover,
.drop-zone.drag-active {
    border-color: var(--accent-color);
    background-color: rgba(59, 130, 246, 0.06);
}

.drop-zone-icon {
    font-size: 2rem;
    margin-bottom: 0.5rem;
}

.drop-zone-primary {
    font-size: 0.95rem;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
}

.drop-zone-link {
    color: var(--accent-color);
    text-decoration: underline;
    cursor: pointer;
}

.drop-zone-secondary {
    font-size: 0.78rem;
    color: var(--text-secondary);
}

/* File preview inside drop zone */
.file-preview {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-top: 1rem;
    padding: 0.6rem 0.75rem;
    background-color: var(--bg-color);
    border-radius: 8px;
    border: 1px solid var(--border-color);
    text-align: left;
}

.file-preview-icon {
    font-size: 1.5rem;
    flex-shrink: 0;
}

.file-preview-info {
    flex: 1;
    min-width: 0;
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.file-preview-name {
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.file-preview-size {
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.file-clear-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    font-size: 0.9rem;
    padding: 2px 6px;
    border-radius: 4px;
    transition: color 0.2s;
    flex-shrink: 0;
}

.file-clear-btn:hover {
    color: var(--danger);
}

/* --- Modal prompt section --- */
.modal-prompt-section {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.modal-label {
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--text-primary);
}

.optional-label {
    color: var(--text-secondary);
    font-weight: 400;
}

.modal-prompt-input {
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    color: var(--text-primary);
    font-family: inherit;
    font-size: 0.9rem;
    padding: 0.65rem 0.75rem;
    resize: none;
    outline: none;
    transition: border-color 0.2s, box-shadow 0.2s;
}

.modal-prompt-input:focus {
    border-color: var(--accent-color);
    box-shadow: 0 0 0 2px rgba(59, 130, 246, 0.2);
}

/* --- Modal footer --- */
.modal-footer {
    display: flex;
    justify-content: flex-end;
    gap: 0.75rem;
}