frontend/css/style.css

/* ============================================================
   OpenMind Chat UI - Premium Design System
   ============================================================ */

/* ─── CSS Variables (Design Tokens) ─────────────────────── */
:root {
    /* Colors - Dark Theme (Default) */
    --bg-primary: #0f0f11;
    --bg-secondary: #1a1a1f;
    --bg-tertiary: #222228;
    --bg-hover: #2a2a32;
    --bg-active: #32323c;

    --surface-1: #1e1e24;
    --surface-2: #26262e;
    --surface-3: #2e2e38;

    --text-primary: #f0f0f5;
    --text-secondary: #a0a0b0;
    --text-tertiary: #6a6a7a;
    --text-inverse: #0f0f11;

    --accent-primary: #6366f1;
    --accent-secondary: #8b5cf6;
    --accent-tertiary: #a78bfa;
    --accent-glow: rgba(99, 102, 241, 0.15);
    --accent-gradient: linear-gradient(135deg, #6366f1 0%, #8b5cf6 50%, #a78bfa 100%);

    --border-color: rgba(255, 255, 255, 0.08);
    --border-hover: rgba(255, 255, 255, 0.15);

    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.5);
    --shadow-glow: 0 0 20px rgba(99, 102, 241, 0.2);

    --user-bubble-bg: #6366f1;
    --assistant-bubble-bg: var(--surface-2);

    --scrollbar-track: transparent;
    --scrollbar-thumb: rgba(255, 255, 255, 0.1);
    --scrollbar-thumb-hover: rgba(255, 255, 255, 0.2);

    /* Sizing */
    --sidebar-width: 280px;
    --input-max-width: 768px;

    /* Transitions */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 400ms cubic-bezier(0.4, 0, 0.2, 1);

    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.8125rem;
    --font-size-base: 0.9375rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.5rem;
    --font-size-2xl: 2rem;

    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 20px;
    --radius-full: 9999px;
}

/* Light Theme */
[data-theme="light"] {
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-tertiary: #f0f1f3;
    --bg-hover: #e8e9ec;
    --bg-active: #dddee2;

    --surface-1: #ffffff;
    --surface-2: #f4f4f6;
    --surface-3: #eaeaee;

    --text-primary: #111118;
    --text-secondary: #555566;
    --text-tertiary: #888899;
    --text-inverse: #ffffff;

    --border-color: rgba(0, 0, 0, 0.08);
    --border-hover: rgba(0, 0, 0, 0.15);

    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.06);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.12);
    --shadow-glow: 0 0 20px rgba(99, 102, 241, 0.1);

    --user-bubble-bg: #6366f1;
    --assistant-bubble-bg: var(--surface-2);

    --scrollbar-track: transparent;
    --scrollbar-thumb: rgba(0, 0, 0, 0.12);
    --scrollbar-thumb-hover: rgba(0, 0, 0, 0.2);
}

/* ─── Reset & Base ──────────────────────────────────────── */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-family);
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow: hidden;
    height: 100vh;
}

/* Custom Scrollbar */
::-webkit-scrollbar {
    width: 6px;
}
::-webkit-scrollbar-track {
    background: var(--scrollbar-track);
}
::-webkit-scrollbar-thumb {
    background: var(--scrollbar-thumb);
    border-radius: var(--radius-full);
}
::-webkit-scrollbar-thumb:hover {
    background: var(--scrollbar-thumb-hover);
}

/* ─── Layout ────────────────────────────────────────────── */
#app {
    display: flex;
    height: 100vh;
    width: 100vw;
    overflow: hidden;
}

/* ─── Sidebar ───────────────────────────────────────────── */
.sidebar {
    width: var(--sidebar-width);
    min-width: var(--sidebar-width);
    height: 100vh;
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    transition: transform var(--transition-base), opacity var(--transition-base);
    z-index: 100;
}

.sidebar-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px;
    border-bottom: 1px solid var(--border-color);
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
}

.logo-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    border-radius: var(--radius-md);
    background: var(--accent-gradient);
    color: white;
}

.logo-text {
    font-size: var(--font-size-lg);
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.btn-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
    background: transparent;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

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

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

.sidebar-search {
    padding: 12px 16px;
}

.search-input {
    width: 100%;
    padding: 8px 12px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
    background: var(--bg-tertiary);
    color: var(--text-primary);
    font-family: var(--font-family);
    font-size: var(--font-size-sm);
    outline: none;
    transition: all var(--transition-fast);
}

.search-input:focus {
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.search-input::placeholder {
    color: var(--text-tertiary);
}

.sidebar-conversations {
    flex: 1;
    overflow-y: auto;
    padding: 8px;
}

.conversation-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 12px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
    border: none;
    background: transparent;
    width: 100%;
    text-align: left;
}

.conversation-item:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
}

.conversation-item.active {
    background: var(--bg-active);
    color: var(--text-primary);
}

.conversation-item .conv-icon {
    flex-shrink: 0;
    opacity: 0.5;
}

.conversation-item .conv-title {
    flex: 1;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.conversation-item .conv-delete {
    opacity: 0;
    flex-shrink: 0;
    transition: opacity var(--transition-fast);
    color: var(--text-tertiary);
    background: none;
    border: none;
    cursor: pointer;
    padding: 2px;
    border-radius: 4px;
}

.conversation-item:hover .conv-delete {
    opacity: 1;
}

.conversation-item .conv-delete:hover {
    color: #ef4444;
}

.sidebar-footer {
    padding: 12px 16px;
    border-top: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.sidebar-footer-btn {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 12px;
    border-radius: var(--radius-sm);
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-family: var(--font-family);
    font-size: var(--font-size-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
    width: 100%;
}

.sidebar-footer-btn:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
}

/* ─── Main Chat Area ────────────────────────────────────── */
.chat-main {
    flex: 1;
    display: flex;
    flex-direction: column;
    height: 100vh;
    min-width: 0;
    position: relative;
}

/* ─── Welcome Screen ────────────────────────────────────── */
.welcome-screen {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 24px;
}

.welcome-screen.hidden {
    display: none;
}

.welcome-content {
    text-align: center;
    max-width: 720px;
    width: 100%;
    animation: fadeInUp 0.6s ease-out;
}

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

.welcome-logo {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 80px;
    height: 80px;
    border-radius: var(--radius-xl);
    background: var(--surface-2);
    margin-bottom: 24px;
    position: relative;
    color: var(--accent-primary);
}

.welcome-logo-glow {
    position: absolute;
    inset: -20px;
    border-radius: 50%;
    background: radial-gradient(circle, var(--accent-glow) 0%, transparent 70%);
    animation: pulse 3s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 0.5; transform: scale(1); }
    50% { opacity: 1; transform: scale(1.1); }
}

.welcome-title {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    margin-bottom: 8px;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.welcome-subtitle {
    font-size: var(--font-size-base);
    color: var(--text-secondary);
    margin-bottom: 40px;
}

.welcome-suggestions {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
    max-width: 600px;
    margin: 0 auto;
}

.suggestion-card {
    display: flex;
    align-items: flex-start;
    gap: 12px;
    padding: 16px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background: var(--surface-1);
    cursor: pointer;
    text-align: left;
    transition: all var(--transition-fast);
    font-family: var(--font-family);
}

.suggestion-card:hover {
    background: var(--bg-hover);
    border-color: var(--accent-primary);
    box-shadow: var(--shadow-glow);
    transform: translateY(-2px);
}

.suggestion-icon {
    font-size: 1.25rem;
    flex-shrink: 0;
    margin-top: 2px;
}

.suggestion-text {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.suggestion-title {
    font-size: var(--font-size-sm);
    font-weight: 600;
    color: var(--text-primary);
}

.suggestion-desc {
    font-size: var(--font-size-xs);
    color: var(--text-tertiary);
}

/* ─── Chat Messages ─────────────────────────────────────── */
.chat-messages {
    flex: 1;
    overflow-y: auto;
    padding: 24px 0;
    display: none;
    flex-direction: column;
}

.chat-messages.active {
    display: flex;
}

.message {
    padding: 12px 24px;
    display: flex;
    gap: 16px;
    max-width: var(--input-max-width);
    width: 100%;
    margin: 0 auto;
    animation: messageIn 0.3s ease-out;
}

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

.message-avatar {
    flex-shrink: 0;
    width: 32px;
    height: 32px;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: var(--font-size-sm);
    font-weight: 600;
}

.message.user .message-avatar {
    background: var(--accent-gradient);
    color: white;
}

.message.assistant .message-avatar {
    background: var(--surface-3);
    color: var(--accent-primary);
}

.message-content {
    flex: 1;
    min-width: 0;
}

.message-role {
    font-size: var(--font-size-sm);
    font-weight: 600;
    margin-bottom: 4px;
    color: var(--text-primary);
}

.message-text {
    font-size: var(--font-size-base);
    line-height: 1.7;
    color: var(--text-primary);
    word-wrap: break-word;
}

.message-text p {
    margin-bottom: 12px;
}

.message-text p:last-child {
    margin-bottom: 0;
}

.message-text code {
    background: var(--surface-3);
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 0.85em;
    font-family: 'JetBrains Mono', 'Fira Code', monospace;
}

.message-text pre {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 16px;
    overflow-x: auto;
    margin: 12px 0;
    position: relative;
}

.message-text pre code {
    background: none;
    padding: 0;
    font-size: 0.85em;
    color: var(--text-primary);
}

/* Typing indicator */
.typing-indicator {
    display: inline-flex;
    gap: 4px;
    align-items: center;
    padding: 4px 0;
}

.typing-indicator .dot {
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--accent-primary);
    animation: typingBounce 1.4s infinite;
}

.typing-indicator .dot:nth-child(2) { animation-delay: 0.2s; }
.typing-indicator .dot:nth-child(3) { animation-delay: 0.4s; }

@keyframes typingBounce {
    0%, 60%, 100% { transform: translateY(0); opacity: 0.4; }
    30% { transform: translateY(-6px); opacity: 1; }
}

/* ─── Input Area ────────────────────────────────────────── */
.input-area {
    padding: 0 24px 24px;
    position: relative;
}

.input-container {
    max-width: var(--input-max-width);
    margin: 0 auto;
}

.input-wrapper {
    display: flex;
    align-items: flex-end;
    gap: 8px;
    background: var(--surface-2);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 8px 12px;
    transition: all var(--transition-fast);
    box-shadow: var(--shadow-md);
}

.input-wrapper:focus-within {
    border-color: var(--accent-primary);
    box-shadow: var(--shadow-md), 0 0 0 3px var(--accent-glow);
}

.input-wrapper textarea {
    flex: 1;
    background: transparent;
    border: none;
    outline: none;
    color: var(--text-primary);
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.5;
    resize: none;
    max-height: 200px;
    padding: 4px 0;
}

.input-wrapper textarea::placeholder {
    color: var(--text-tertiary);
}

.input-actions {
    display: flex;
    align-items: center;
    gap: 4px;
}

.btn-send {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    border-radius: var(--radius-sm);
    border: none;
    background: var(--accent-gradient);
    color: white;
    cursor: pointer;
    transition: all var(--transition-fast);
    flex-shrink: 0;
}

.btn-send:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-glow);
}

.btn-send:disabled {
    opacity: 0.3;
    cursor: not-allowed;
    transform: none;
}

.stop-btn {
    border: none;
    background: #ef4444;
    color: white;
}

.stop-btn:hover {
    background: #dc2626;
    color: white;
}

.input-disclaimer {
    text-align: center;
    font-size: var(--font-size-xs);
    color: var(--text-tertiary);
    margin-top: 8px;
}

.hidden {
    display: none !important;
}

/* ─── Settings Panel ────────────────────────────────────── */
.settings-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(4px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 200;
    animation: fadeIn 0.2s ease-out;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.settings-panel {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    width: 480px;
    max-width: 90vw;
    max-height: 85vh;
    overflow-y: auto;
    box-shadow: var(--shadow-lg);
    animation: slideUp 0.3s ease-out;
}

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

.settings-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 20px 24px;
    border-bottom: 1px solid var(--border-color);
}

.settings-header h2 {
    font-size: var(--font-size-lg);
    font-weight: 600;
}

.settings-body {
    padding: 24px;
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.settings-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.settings-label {
    font-size: var(--font-size-sm);
    font-weight: 500;
    color: var(--text-secondary);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.settings-value {
    font-weight: 600;
    color: var(--accent-primary);
    font-size: var(--font-size-sm);
}

.settings-select,
.settings-input {
    padding: 10px 12px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
    background: var(--bg-tertiary);
    color: var(--text-primary);
    font-family: var(--font-family);
    font-size: var(--font-size-sm);
    outline: none;
    transition: all var(--transition-fast);
}

.settings-select:focus,
.settings-input:focus {
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.settings-textarea {
    padding: 10px 12px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
    background: var(--bg-tertiary);
    color: var(--text-primary);
    font-family: var(--font-family);
    font-size: var(--font-size-sm);
    outline: none;
    resize: vertical;
    transition: all var(--transition-fast);
}

.settings-textarea:focus {
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.settings-slider {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 6px;
    border-radius: var(--radius-full);
    background: var(--bg-tertiary);
    outline: none;
    transition: background var(--transition-fast);
}

.settings-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: var(--accent-primary);
    cursor: pointer;
    box-shadow: 0 0 8px rgba(99, 102, 241, 0.4);
    transition: all var(--transition-fast);
}

.settings-slider::-webkit-slider-thumb:hover {
    transform: scale(1.15);
}

.slider-labels {
    display: flex;
    justify-content: space-between;
    font-size: var(--font-size-xs);
    color: var(--text-tertiary);
}

/* ─── Mobile Menu Button ────────────────────────────────── */
.mobile-menu-btn {
    display: none;
    position: fixed;
    top: 12px;
    left: 12px;
    z-index: 150;
    width: 40px;
    height: 40px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
    background: var(--bg-secondary);
    color: var(--text-primary);
    cursor: pointer;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
}

.mobile-menu-btn:hover {
    background: var(--bg-hover);
}

/* ─── Responsive ────────────────────────────────────────── */
@media (max-width: 768px) {
    .sidebar {
        position: fixed;
        left: 0;
        top: 0;
        transform: translateX(-100%);
        box-shadow: var(--shadow-lg);
    }

    .sidebar.open {
        transform: translateX(0);
    }

    .mobile-menu-btn {
        display: flex;
    }

    .welcome-suggestions {
        grid-template-columns: 1fr;
    }

    .welcome-title {
        font-size: var(--font-size-xl);
    }

    .message {
        padding: 12px 16px;
    }

    .input-area {
        padding: 0 12px 16px;
    }
}

@media (max-width: 480px) {
    .settings-panel {
        width: 100%;
        max-width: 100%;
        height: 100%;
        max-height: 100%;
        border-radius: 0;
    }
}