/* style.css */

/* ------------------- */
/* CSS Variables & Setup */
/* ------------------- */
:root {
    --font-family-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    
    /* Light Theme */
    --bg-primary: #f4f7f9;
    --bg-secondary: #ffffff;
    --surface: #ffffff;
    --text-primary: #1a202c;
    --text-secondary: #4a5568;
    --border-color: #e2e8f0;
    --accent-primary: #3b82f6;
    --accent-primary-hover: #2563eb;
    --accent-danger: #ef4444;
    --accent-danger-hover: #dc2626;
    --shadow-color: 220, 230, 240;
    
    /* Sizing & Spacing */
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 16px;
    --spacing-lg: 24px;
    --spacing-xl: 32px;
    --border-radius: 8px;
    --transition: 0.2s ease-in-out;
}

.dark-mode {
    /* Dark Theme */
    --bg-primary: #121828;
    --bg-secondary: #1a2235;
    --surface: #202940;
    --text-primary: #f0f4f8;
    --text-secondary: #a0aec0;
    --border-color: #2d3748;
    --accent-primary: #4f8ff7;
    --accent-primary-hover: #68a3ff;
    --shadow-color: 0, 0, 0;
}

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

body {
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-family: var(--font-family-sans);
    line-height: 1.6;
    transition: background-color var(--transition), color var(--transition);
}

[x-cloak] { display: none !important; }

/* ------------------- */
/* Layout */
/* ------------------- */
.app-layout {
    display: flex;
    min-height: 100vh;
}

.sidebar {
    background-color: var(--bg-secondary);
    width: 260px;
    flex-shrink: 0;
    border-right: 1px solid var(--border-color);
    transition: width var(--transition);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    padding: var(--spacing-md);
}

.sidebar--collapsed {
    width: 80px;
}

.sidebar__header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-xl);
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--accent-primary);
    cursor: pointer;
}

.sidebar__nav {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.nav-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--border-radius);
    color: var(--text-secondary);
    font-weight: 500;
    cursor: pointer;
    transition: background-color var(--transition), color var(--transition);
}

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

.nav-item.active {
    background-color: var(--accent-primary);
    color: white;
}

.sidebar--collapsed .nav-item span {
    display: none;
}
.sidebar--collapsed .nav-item {
    justify-content: center;
}

.main {
    flex-grow: 1;
    padding: var(--spacing-xl);
    overflow-y: auto;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
}

/* Page Headers */
.page-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: var(--spacing-xs);
}
.page-subtitle {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
}
.page-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-lg);
}

/* Grids */
.grid-layout {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
}

/* Spacing & Flex Helpers */
.mb-md { margin-bottom: var(--spacing-md); }
.mb-lg { margin-bottom: var(--spacing-lg); }
.space-y-md { display: flex; flex-direction: column; gap: var(--spacing-md); }
.space-y-lg { display: flex; flex-direction: column; gap: var(--spacing-lg); }
.flex { display: flex; }
.items-center { align-items: center; }
.gap-md { gap: var(--spacing-md); }

/* ------------------- */
/* Components */
/* ------------------- */

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 0.9rem;
    font-weight: 600;
    border-radius: var(--border-radius);
    border: 1px solid transparent;
    cursor: pointer;
    transition: all var(--transition);
    text-decoration: none;
    white-space: nowrap;
}
.btn--sm { padding: var(--spacing-xs) var(--spacing-sm); font-size: 0.8rem; }
.btn--full-width { width: 100%; }
.btn--icon {
    padding: var(--spacing-sm);
    background-color: transparent;
    border-color: transparent;
    color: var(--text-secondary);
}
.btn--icon:hover { background-color: var(--bg-primary); color: var(--text-primary); }
.btn--icon.btn--danger:hover { color: var(--accent-danger); }
.btn--icon.rotate-180 { transform: rotate(180deg); }

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

.btn--secondary { background-color: var(--surface); color: var(--text-primary); border: 1px solid var(--border-color); }
.btn--secondary:hover { background-color: var(--bg-primary); }
.dark-mode .btn--secondary:hover { background-color: var(--border-color); }

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

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

.btn--danger-outline { background-color: transparent; color: var(--accent-danger); border-color: var(--accent-danger); }
.btn--danger-outline:hover { background-color: var(--accent-danger); color: white; }

.button-group { display: flex; gap: var(--spacing-sm); }

/* Cards */
.card {
    background-color: var(--surface);
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    box-shadow: 0 4px 6px -1px rgba(var(--shadow-color), 0.1), 0 2px 4px -1px rgba(var(--shadow-color), 0.06);
    transition: all var(--transition);
}
.card--interactive:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 15px -3px rgba(var(--shadow-color), 0.1), 0 4px 6px -2px rgba(var(--shadow-color), 0.05);
    cursor: pointer;
}
.card__header { padding: var(--spacing-md); border-bottom: 1px solid var(--border-color); display: flex; justify-content: space-between; align-items: center; }
.card__body { padding: var(--spacing-md); }
.card__title { font-size: 1.1rem; font-weight: 600; margin-bottom: 4px; }
.card__subtitle { font-size: 0.9rem; color: var(--text-secondary); margin-bottom: var(--spacing-md); }

/* Progress Bar */
.progress-wrapper { background-color: var(--bg-primary); border-radius: 99px; height: 8px; overflow: hidden; margin-top: var(--spacing-md); }
.progress-bar { background-color: #38a169; height: 100%; border-radius: 99px; transition: width 0.5s ease; }
.course-meta { font-size: 0.85rem; color: var(--text-secondary); display: flex; justify-content: space-between; margin-top: var(--spacing-md); }

/* Forms */
.form-group { margin-bottom: var(--spacing-md); }
.form-label { display: block; font-weight: 500; margin-bottom: var(--spacing-sm); }
.form-control { width: 100%; padding: var(--spacing-sm) var(--spacing-md); border: 1px solid var(--border-color); border-radius: var(--border-radius); background-color: var(--bg-primary); color: var(--text-primary); font-size: 1rem; transition: border-color var(--transition), box-shadow var(--transition); }
.form-control:focus { outline: none; border-color: var(--accent-primary); box-shadow: 0 0 0 3px rgba(var(--accent-primary), 0.2); }
textarea.form-control { resize: vertical; min-height: 80px; }
.form-hint { font-size: 0.8rem; color: var(--text-secondary); margin-top: var(--spacing-xs); }
.checkbox-label { display: flex; align-items: center; gap: var(--spacing-sm); cursor: pointer; }
hr { border: none; border-top: 1px solid var(--border-color); margin: var(--spacing-lg) 0; }

/* Modal */
.modal { position: fixed; inset: 0; background-color: rgba(0,0,0,0.5); display: flex; align-items: center; justify-content: center; z-index: 1000; }
.modal__dialog { background-color: var(--bg-secondary); border-radius: var(--border-radius); width: 90%; max-width: 600px; max-height: 90vh; overflow-y: auto; animation: modal-fade-in 0.3s ease; }
.modal-content { padding: var(--spacing-lg); }
.modal-title { font-size: 1.5rem; margin-bottom: var(--spacing-lg); }
.modal-actions { margin-top: var(--spacing-lg); display: flex; justify-content: flex-end; gap: var(--spacing-md); }

/* Flashcards */
.flashcard-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: var(--spacing-md); }
.flashcard { aspect-ratio: 3 / 2; perspective: 1000px; position: relative; }
.flashcard__face { position: absolute; width: 100%; height: 100%; backface-visibility: hidden; transition: transform 0.6s; transform-style: preserve-3d; border-radius: var(--border-radius); padding: var(--spacing-md); display: flex; align-items: center; justify-content: center; text-align: center; cursor: pointer; font-size: 0.9rem; border: 1px solid var(--border-color); }
.flashcard__front { background-color: var(--surface); }
.flashcard__back { background-color: var(--bg-primary); transform: rotateY(180deg); }
.flashcard.is-flipped .flashcard__front { transform: rotateY(180deg); }
.flashcard.is-flipped .flashcard__back { transform: rotateY(360deg); }
.flashcard__actions { position: absolute; top: var(--spacing-sm); right: var(--spacing-sm); display: flex; gap: var(--spacing-xs); z-index: 10; opacity: 0; transition: opacity var(--transition); }
.flashcard:hover .flashcard__actions { opacity: 1; }
.flashcard__actions .btn { background-color: rgba(255, 255, 255, 0.7); }
.dark-mode .flashcard__actions .btn { background-color: rgba(0, 0, 0, 0.4); }

/* Other */
.bullet-list { list-style-position: inside; padding-left: var(--spacing-sm); }
.empty-state { color: var(--text-secondary); text-align: center; padding: var(--spacing-lg); grid-column: 1 / -1; }

/* Animations */
@keyframes modal-fade-in { from { opacity: 0; transform: scale(0.95); } to { opacity: 1; transform: scale(1); } }
.fade-in { animation: fade-in 0.5s ease; }
@keyframes fade-in { from { opacity: 0; transform: translateY(10px); } to { opacity: 1; transform: translateY(0); } }

/* Quill Editor Overrides */
.ql-toolbar { border-top-left-radius: var(--border-radius); border-top-right-radius: var(--border-radius); border-color: var(--border-color) !important; }
.ql-container { border-bottom-left-radius: var(--border-radius); border-bottom-right-radius: var(--border-radius); border-color: var(--border-color) !important; background-color: var(--bg-primary); color: var(--text-primary); font-family: var(--font-family-sans); font-size: 1rem; }
.dark-mode .ql-snow .ql-stroke { stroke: var(--text-secondary); }
.dark-mode .ql-snow .ql-picker-label { color: var(--text-secondary); }
.dark-mode .ql-snow .ql-fill { fill: var(--text-secondary); }

/* Sidebar Course List */
.sidebar__courses { margin-top: var(--spacing-lg); display: flex; flex-direction: column; gap: var(--spacing-xs); max-height: 40vh; overflow-y: auto; }
.sidebar__courses-title { font-size: 0.8rem; font-weight: 600; text-transform: uppercase; color: var(--text-secondary); padding: 0 var(--spacing-md); margin-bottom: var(--spacing-sm); }
.nav-item--sub { font-size: 0.9rem; padding-left: var(--spacing-md); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.nav-item--sub .course-code { font-weight: 600; color: var(--accent-primary); flex-shrink: 0; }
.dark-mode .nav-item--sub.active { background-color: var(--accent-primary); color: white; }
.dark-mode .nav-item--sub.active .course-code { color: white; }

/* Breadcrumbs */
.breadcrumbs { display: flex; align-items: center; gap: var(--spacing-sm); margin-bottom: var(--spacing-md); font-size: 0.9rem; color: var(--text-secondary); }
.breadcrumbs a { color: var(--accent-primary); text-decoration: none; cursor: pointer; }
.breadcrumbs a:hover { text-decoration: underline; }

/* List Views */
.list-container { display: flex; flex-direction: column; gap: var(--spacing-md); }
.list-item-card { display: flex; justify-content: space-between; align-items: center; background-color: var(--surface); padding: var(--spacing-md); border-radius: var(--border-radius); border: 1px solid var(--border-color); transition: all var(--transition); cursor: pointer; }

/* Expandable Card */
.expandable-card { background-color: var(--surface); border-radius: var(--border-radius); border: 1px solid var(--border-color); overflow: hidden; }
.expandable-card .list-item-card { border: none; border-bottom: 1px solid var(--border-color); border-radius: 0; }
.expandable-content { background-color: var(--bg-primary); padding: var(--spacing-md); }
.nested-list { display: flex; flex-direction: column; gap: var(--spacing-sm); }
.nested-list-item { display: flex; justify-content: space-between; align-items: center; background-color: var(--surface); padding: var(--spacing-sm) var(--spacing-md); border-radius: var(--border-radius); }
.add-button-footer { border-top: 1px solid var(--border-color); margin-top: var(--spacing-md); padding-top: var(--spacing-md); text-align: center; }

/* Sortable (Drag & Drop) */
.drag-handle { cursor: grab; color: var(--text-secondary); padding-right: var(--spacing-sm); }
.sortable-ghost { opacity: 0.5; background: var(--accent-primary); color: white; }
.sortable-drag { box-shadow: 0 10px 15px -3px rgba(var(--shadow-color), 0.2), 0 4px 6px -2px rgba(var(--shadow-color), 0.1); }

/* Note List Item */
.note-list { display: flex; flex-direction: column; gap: var(--spacing-sm); }
.list-item { display: flex; justify-content: space-between; align-items: center; background-color: var(--bg-primary); padding: var(--spacing-sm) var(--spacing-md); border-radius: var(--border-radius); border: 1px solid var(--border-color); }

/* Status Indicator */
.status-select { -webkit-appearance: none; -moz-appearance: none; appearance: none; border: none; background-color: transparent; padding: 6px 24px 6px 12px; border-radius: 99px; font-weight: 600; font-size: 0.8rem; cursor: pointer; background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 20 20'%3e%3cpath stroke='%236b7280' stroke-linecap='round' stroke-linejoin='round' stroke-width='1.5' d='M6 8l4 4 4-4'/%3e%3c/svg%3e"); background-position: right 6px center; background-repeat: no-repeat; background-size: 16px; }
.dark-mode .status-select { background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 20 20'%3e%3cpath stroke='%239CA3AF' stroke-linecap='round' stroke-linejoin='round' stroke-width='1.5' d='M6 8l4 4 4-4'/%3e%3c/svg%3e"); }

.status--unread { background-color: #e2e8f0; color: #4a5568; }
.status--confused { background-color: #feebc8; color: #9c4221; }
.status--revised { background-color: #c6f6d5; color: #2f855a; }
.dark-mode .status--unread { background-color: #4a5568; color: #e2e8f0; }
.dark-mode .status--confused { background-color: #9c4221; color: #feebc8; }
.dark-mode .status--revised { background-color: #2f855a; color: #c6f6d5; }

/* Subtopic Content Layout */
.subtopic-content-layout { display: grid; grid-template-columns: 1fr; gap: var(--spacing-lg); }
@media (min-width: 1024px) { .subtopic-content-layout { grid-template-columns: repeat(2, 1fr); } }