:root {
    --bg-primary: #000000;
    --bg-secondary: #000000;
    --bg-tertiary: #000000;
    --text-primary: #ffffff;
    --text-secondary: #a0a0a0;
    --text-tertiary: #606060;
    --border: rgba(255, 255, 255, 0.1);
    --glass: rgba(255, 255, 255, 0.05);
    --glass-border: rgba(255, 255, 255, 0.1);
    --accent: rgba(255, 255, 255, 0.6);
    --accent-hover: rgba(255, 255, 255, 0.7);
    --sidebar-width: 180px;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    height: 100vh;
    display: flex;
    overflow: hidden;
    -webkit-font-smoothing: antialiased;
    margin: 0; padding: 0; border: none;
}

.glass {
    background: var(--glass);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--glass-border);
}

.tutor-side-panel {
    width: 180px; min-width: 180px;
    background: var(--bg-secondary);
    display: flex; flex-direction: column;
    flex-shrink: 0;
    border-right: 1px solid var(--border);
    position: relative; z-index: 100;
}

.sidebar-header {
    padding: 16px;
    border-bottom: 1px solid var(--border);
    display: flex; flex-direction: column;
    gap: 12px; flex-shrink: 0;
}

.new-study-session-btn {
    width: 100%; height: 40px;
    background: transparent;
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--text-primary);
    font-size: 14px; font-weight: 400;
    cursor: pointer;
    display: flex; align-items: center;
    justify-content: flex-start;
    gap: 12px; padding: 0 12px;
    transition: background 0.15s;
}
.new-study-session-btn:hover { background: rgba(255,255,255,0.05); }

.new-session-icon { width: 20px; height: 20px; display: flex; align-items: center; justify-content: center; flex-shrink: 0; }
.new-session-icon svg { width: 20px; height: 20px; display: block; }
.new-session-label { font-size: 14px; }

.sidebar-search-wrapper { position: relative; width: 100%; }
.sidebar-search {
    width: 100%; height: 40px;
    background: transparent;
    border: 1px solid var(--border);
    border-radius: 8px;
    color: var(--text-primary);
    font-size: 13px;
    padding: 0 12px 0 44px;
    outline: none; font-family: inherit;
}
.sidebar-search::placeholder { color: var(--text-tertiary); }
.sidebar-search-icon {
    position: absolute; left: 14px; top: 50%; transform: translateY(-50%);
    color: var(--text-tertiary); pointer-events: none;
    width: 20px; height: 20px; display: flex; align-items: center; justify-content: center;
}
.sidebar-search-icon svg { width: 20px; height: 20px; display: block; }

.tutor-sessions-list {
    flex: 1; overflow-y: auto; overflow-x: hidden;
    padding: 8px; scrollbar-width: none; -ms-overflow-style: none;
}
.tutor-sessions-list::-webkit-scrollbar { display: none; }

.study-session-item {
    min-height: 44px; padding: 10px 12px; margin-bottom: 4px;
    border-radius: 8px; cursor: pointer; font-size: 13px;
    color: var(--text-secondary); transition: background 0.15s;
    display: flex; justify-content: space-between; align-items: center; gap: 8px;
}
.study-session-item:hover { background: rgba(255,255,255,0.05); }
.study-session-item.active { background: rgba(255,255,255,0.08); color: var(--text-primary); }

.session-item-content { display: flex; align-items: center; gap: 12px; flex: 1; min-width: 0; }
.session-type-icon { width: 20px; height: 20px; display: flex; align-items: center; justify-content: center; flex-shrink: 0; }
.session-type-icon svg { width: 20px; height: 20px; display: block; }
.session-title-text { flex: 1; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; min-width: 0; }

.delete-session-btn {
    opacity: 0; color: var(--text-tertiary); cursor: pointer;
    padding: 6px; transition: opacity 0.15s, color 0.15s;
    font-size: 18px; border-radius: 4px;
    display: flex; align-items: center; justify-content: center;
    width: 24px; height: 24px; flex-shrink: 0;
}
.study-session-item:hover .delete-session-btn { opacity: 1; }
.delete-session-btn:hover { color: #ef4444; background: rgba(239,68,68,0.1); }

.sidebar-footer {
    border-top: 1px solid var(--border);
    padding: 12px; flex-shrink: 0;
    display: flex; flex-direction: column; gap: 6px;
}

.sidebar-footer-btn {
    width: 100%; height: 40px;
    background: transparent; border: none;
    border-radius: 8px; color: var(--text-secondary);
    font-size: 13px; cursor: pointer;
    display: flex; align-items: center;
    justify-content: flex-start;
    gap: 12px; padding: 0 12px;
    transition: all 0.15s;
}
.sidebar-footer-btn:hover { background: rgba(255,255,255,0.05); color: var(--text-primary); }
.sidebar-footer-icon { width: 20px; height: 20px; display: flex; align-items: center; justify-content: center; flex-shrink: 0; }
.sidebar-footer-icon svg { width: 20px; height: 20px; display: block; }
.sidebar-footer-text { font-size: 13px; }
.user-profile-btn { justify-content: flex-start; }

.main-content { flex: 1; display: flex; flex-direction: column; overflow: hidden; position: relative; }

.top-bar {
    padding: 0 24px;
    display: flex; justify-content: space-between; align-items: center;
    border-bottom: 1px solid var(--border);
    background: var(--bg-primary);
    height: 64px; flex-shrink: 0;
}

.app-title { font-size: 16px; font-weight: 500; color: var(--text-primary); }

.model-badge {
    padding: 6px 12px;
    background: rgba(255,255,255,0.05);
    border: 1px solid var(--border);
    border-radius: 6px; font-size: 11px;
    color: var(--text-secondary); font-weight: 400;
}

.provider-dropdown { position: relative; }

.provider-dropdown-btn {
    height: 32px; padding: 0 10px;
    background: transparent;
    border: 1px solid var(--border);
    border-radius: 8px; color: var(--text-secondary);
    font-size: 12px; cursor: pointer;
    display: flex; align-items: center; gap: 7px;
    font-family: inherit; transition: all 0.15s;
}
.provider-dropdown-btn:hover { background: rgba(255,255,255,0.05); color: var(--text-primary); }

.provider-logo-wrapper { width: 14px; height: 14px; display: flex; align-items: center; justify-content: center; flex-shrink: 0; }
.provider-logo-wrapper svg { width: 14px; height: 14px; }
.provider-logo { width: 14px; height: 14px; flex-shrink: 0; }

.provider-dropdown-menu {
    display: none; position: absolute;
    top: calc(100% + 6px); left: 0;
    background: #111111;
    border: 1px solid var(--border);
    border-radius: 10px; overflow: hidden;
    min-width: 150px; z-index: 9999;
    box-shadow: 0 8px 24px rgba(0,0,0,0.6);
    animation: dropdownFade 0.15s ease-out;
}
.provider-dropdown-menu.open { display: block; }

@keyframes dropdownFade {
    from { opacity: 0; transform: translateY(-4px); }
    to { opacity: 1; transform: translateY(0); }
}

.provider-dropdown-item {
    display: flex; align-items: center; gap: 8px;
    padding: 10px 14px; font-size: 13px;
    color: var(--text-secondary); cursor: pointer;
    transition: background 0.1s;
}
.provider-dropdown-item:hover { background: rgba(255,255,255,0.06); color: var(--text-primary); }
.provider-dropdown-item.active { color: var(--text-primary); }
.check-icon { margin-left: auto; opacity: 0; flex-shrink: 0; }
.provider-dropdown-item.active .check-icon { opacity: 1; }

.conversation-thread { flex: 1; overflow-y: auto; scroll-behavior: smooth; will-change: scroll-position; }
.conversation-thread::-webkit-scrollbar { width: 6px; }
.conversation-thread::-webkit-scrollbar-track { background: transparent; }
.conversation-thread::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.1); border-radius: 3px; }

.message-container { max-width: 48rem; margin: 0 auto; padding: 24px 16px 20px; }

.message-wrapper {
    margin-bottom: 24px; display: flex;
    flex-direction: column; gap: 8px;
    animation: messageSlide 0.3s ease-out;
}
@keyframes messageSlide {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
}
.message-wrapper.user { align-items: flex-end; }
.message-wrapper.assistant { align-items: flex-start; }
.message-role { font-size: 12px; color: var(--text-tertiary); font-weight: 500; padding: 0 4px; }
.message-content { max-width: 85%; }
.message-bubble { font-size: 15px; line-height: 1.6; word-wrap: break-word; color: var(--text-primary); padding: 2px 0; }
.message-bubble p { margin: 0 0 8px 0; }
.message-bubble p:last-child { margin-bottom: 0; }
.message-bubble code { background: rgba(255,255,255,0.1); padding: 2px 6px; border-radius: 4px; font-family: 'SF Mono','Monaco','Consolas',monospace; font-size: 0.9em; }
.message-bubble pre { background: rgba(255,255,255,0.05); border: 1px solid var(--border); border-radius: 8px; padding: 16px; overflow-x: auto; margin: 12px 0; }
.message-bubble pre code { background: none; padding: 0; border: none; }
.message-image { max-width: 100%; max-height: 400px; border-radius: 8px; margin-bottom: 8px; border: 1px solid var(--border); }

.typing-dots { display: inline-flex; gap: 6px; padding: 12px 16px; }
.typing-dots span { width: 6px; height: 6px; background: rgba(255,255,255,0.6); border-radius: 50%; animation: typingBounce 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 typingBounce {
    0%, 60%, 100% { transform: translateY(0); opacity: 0.4; }
    30% { transform: translateY(-8px); opacity: 1; }
}

.input-area { padding: 8px 8px 60px 8px; background: transparent; flex-shrink: 0; }
.input-container { max-width: 48rem; margin: 0 auto; }

.input-wrapper {
    background: var(--glass);
    backdrop-filter: blur(20px); -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--glass-border);
    border-radius: 12px; padding: 10px 14px;
    display: flex; align-items: center; gap: 10px;
    transition: border-color 0.15s;
}
.input-wrapper:focus-within { border-color: rgba(255,255,255,0.25); }

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

.attach-resource-btn {
    width: 32px; height: 32px;
    background: transparent; border: none;
    border-radius: 8px; color: var(--text-tertiary);
    cursor: pointer; display: flex;
    align-items: center; justify-content: center;
    flex-shrink: 0; transition: all 0.15s;
    padding: 0; position: relative;
}
.attach-resource-btn:hover { color: var(--text-secondary); background: rgba(255,255,255,0.05); }
.attach-resource-btn input[type="file"] {
    position: absolute; inset: 0;
    opacity: 0; cursor: pointer;
    width: 100%; height: 100%;
}

.student-query-input {
    flex: 1; background: transparent; border: none;
    color: var(--text-primary); font-size: 15px;
    outline: none; font-family: inherit;
    resize: none; min-height: 24px; max-height: 200px;
    line-height: 24px; padding: 0;
}
.student-query-input::placeholder { color: var(--text-tertiary); }

.ask-tutor-btn {
    width: 32px; height: 32px;
    background: rgba(255,255,255,0.1);
    color: var(--text-primary);
    border: 1px solid var(--border);
    border-radius: 8px; cursor: pointer;
    display: flex; align-items: center; justify-content: center;
    flex-shrink: 0; transition: all 0.2s ease;
}
.ask-tutor-btn:hover:not(:disabled) { background: rgba(255,255,255,0.15); transform: translateY(-1px); }
.ask-tutor-btn:active:not(:disabled) { transform: translateY(0); }
.ask-tutor-btn:disabled { opacity: 0.3; cursor: not-allowed; }
.ask-tutor-btn svg { width: 16px; height: 16px; }

.material-preview-area { padding: 0 4px; }

.empty-state {
    display: flex; flex-direction: column;
    align-items: center; justify-content: center;
    height: 100%; text-align: center; padding: 48px 24px;
}
.empty-icon { width: 48px; height: 48px; color: rgba(255,255,255,0.4); margin-bottom: 16px; opacity: 0.8; }
.empty-icon svg { width: 100%; height: 100%; }
.empty-title { font-size: 28px; font-weight: 600; margin-bottom: 8px; color: var(--text-primary); }
.empty-text { font-size: 15px; color: var(--text-secondary); margin-bottom: 40px; }

.study-prompts-grid {
    display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 12px; max-width: 48rem; width: 100%; margin: 0 auto;
}
.suggestion-card {
    padding: 16px;
    background: rgba(255,255,255,0.03);
    border: 1px solid var(--border);
    border-radius: 12px; cursor: pointer;
    transition: all 0.15s; text-align: left;
}
.suggestion-card:hover { background: rgba(255,255,255,0.05); border-color: rgba(255,255,255,0.2); transform: translateY(-2px); }
.suggestion-icon { width: 20px; height: 20px; margin-bottom: 8px; display: block; color: var(--text-secondary); }
.suggestion-text { font-size: 14px; color: var(--text-secondary); line-height: 1.5; }

.error-message {
    position: fixed; top: 80px; left: 50%; transform: translateX(-50%);
    padding: 12px 20px;
    background: rgba(239,68,68,0.1);
    backdrop-filter: blur(20px); -webkit-backdrop-filter: blur(20px);
    border: 1px solid rgba(239,68,68,0.3);
    border-radius: 8px; color: #ef4444;
    font-size: 14px; z-index: 1000;
    animation: slideDown 0.3s ease-out;
    max-width: 400px; display: flex; align-items: center; gap: 8px;
}
@keyframes slideDown {
    from { opacity: 0; transform: translateX(-50%) translateY(-10px); }
    to { opacity: 1; transform: translateX(-50%) translateY(0); }
}
.error-icon { width: 16px; height: 16px; flex-shrink: 0; }

.settings-modal { display: none; position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0,0,0,0.8); backdrop-filter: blur(8px); z-index: 2000; align-items: center; justify-content: center; }
.settings-modal.active { display: flex; }

.settings-content {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 16px; max-width: 800px; width: 90%;
    max-height: 80vh; overflow: hidden;
    animation: modalSlide 0.3s ease-out;
    display: flex; flex-direction: column;
}
@keyframes modalSlide {
    from { opacity: 0; transform: scale(0.95) translateY(20px); }
    to { opacity: 1; transform: scale(1) translateY(0); }
}

.settings-header { padding: 24px; border-bottom: 1px solid var(--border); display: flex; justify-content: space-between; align-items: center; flex-shrink: 0; }
.settings-title { font-size: 20px; font-weight: 600; color: var(--text-primary); }
.settings-close { width: 32px; height: 32px; background: transparent; border: 1px solid var(--border); color: var(--text-secondary); cursor: pointer; border-radius: 6px; display: flex; align-items: center; justify-content: center; transition: all 0.15s; }
.settings-close:hover { background: rgba(255,255,255,0.1); color: var(--text-primary); }
.settings-main { display: flex; flex: 1; overflow: hidden; }
.settings-sidebar { width: 200px; border-right: 1px solid var(--border); padding: 16px 8px; flex-shrink: 0; overflow-y: auto; }
.settings-nav-item { padding: 10px 12px; margin-bottom: 4px; border-radius: 8px; cursor: pointer; font-size: 14px; color: var(--text-secondary); transition: all 0.15s; display: flex; align-items: center; gap: 10px; }
.settings-nav-item:hover { background: rgba(255,255,255,0.05); color: var(--text-primary); }
.settings-nav-item.active { background: rgba(255,255,255,0.08); color: var(--text-primary); }
.settings-nav-icon { width: 20px; height: 20px; display: flex; align-items: center; justify-content: center; flex-shrink: 0; }
.settings-nav-icon svg { width: 20px; height: 20px; display: block; }
.settings-body { flex: 1; padding: 24px; overflow-y: auto; }
.settings-panel { display: none; }
.settings-panel.active { display: block; animation: panelFade 0.2s ease-out; }
@keyframes panelFade {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
}
.settings-panel-title { font-size: 18px; font-weight: 600; color: var(--text-primary); margin-bottom: 8px; }
.settings-panel-desc { font-size: 13px; color: var(--text-secondary); margin-bottom: 24px; }
.settings-section { margin-bottom: 32px; }
.settings-section:last-child { margin-bottom: 0; }
.settings-option { display: flex; justify-content: space-between; align-items: center; padding: 16px 0; border-bottom: 1px solid var(--border); }
.settings-option:last-child { border-bottom: none; }
.settings-option-label { flex: 1; padding-right: 20px; }
.settings-option-name { font-size: 14px; color: var(--text-primary); margin-bottom: 4px; }
.settings-option-desc { font-size: 12px; color: var(--text-secondary); line-height: 1.5; }
.settings-slider { width: 200px; }
.slider-container { display: flex; flex-direction: column; gap: 8px; }
.slider-header { display: flex; justify-content: space-between; align-items: center; }
.slider-value { font-size: 13px; color: rgba(255,255,255,0.8); font-weight: 500; }
.slider { width: 100%; height: 4px; background: rgba(255,255,255,0.1); border-radius: 2px; outline: none; -webkit-appearance: none; }
.slider::-webkit-slider-thumb { -webkit-appearance: none; width: 16px; height: 16px; background: rgba(255,255,255,0.8); border-radius: 50%; cursor: pointer; transition: all 0.15s; }
.slider::-webkit-slider-thumb:hover { transform: scale(1.2); background: rgba(255,255,255,0.9); }
.slider::-moz-range-thumb { width: 16px; height: 16px; background: rgba(255,255,255,0.8); border-radius: 50%; cursor: pointer; border: none; }
.toggle { position: relative; width: 44px; height: 24px; background: rgba(255,255,255,0.1); border-radius: 12px; cursor: pointer; transition: background 0.2s; flex-shrink: 0; }
.toggle.active { background: rgba(255,255,255,0.3); }
.toggle-slider { position: absolute; top: 2px; left: 2px; width: 20px; height: 20px; background: white; border-radius: 50%; transition: transform 0.2s; }
.toggle.active .toggle-slider { transform: translateX(20px); }
.settings-info-box { background: rgba(255,255,255,0.03); border: 1px solid var(--border); border-radius: 8px; padding: 12px; margin-top: 12px; font-size: 12px; color: var(--text-secondary); line-height: 1.5; }
.settings-info-box strong { color: var(--text-primary); }