/* AI CHANGE: Replaced minimal placeholder CSS with full responsive assignment styling */
/* AI COMMENT: Styles now support responsive cards, enrollment color states, modal, add-course form, and accessible focus/contrast while keeping original file purpose. */

/* AI COMMENT: Root variables centralize colors and spacing tokens so styling stays consistent and easy to tweak. */
:root {
  --bg: #f6f8fb;
  --surface: #ffffff;
  --text: #1f2937;
  --muted: #4b5563;
  --primary: #0f4c81;
  --primary-hover: #0b3a62;
  --border: #d1d5db;
  --ok-bg: #dcfce7;
  --ok-text: #14532d;
  --warn-bg: #fef3c7;
  --warn-text: #78350f;
  --danger-bg: #fee2e2;
  --danger-text: #7f1d1d;
  --shadow: 0 8px 20px rgba(0, 0, 0, 0.08);
}

/* AI COMMENT: Global box-sizing keeps layout math predictable for cards, form fields, and modal elements. */
* {
  box-sizing: border-box;
}

/* AI COMMENT: Base page typography/colors establish a readable default for all sections. */
body {
  margin: 0;
  font-family: "Segoe UI", Tahoma, Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.45;
}

/* AI COMMENT: Header and footer share a light banner style to frame the interactive main content. */
header,
footer {
  padding: 1rem;
  background: #e5edf5;
  border-bottom: 1px solid #c5d4e3;
}

/* AI COMMENT: Footer-specific adjustments separate it visually from the page body. */
footer {
  border-top: 1px solid #c5d4e3;
  border-bottom: 0;
  margin-top: 1rem;
}

/* AI COMMENT: Header content width is constrained to improve readability on large screens. */
.header-content {
  max-width: 1100px;
  margin: 0 auto;
}

/* AI COMMENT: Main container centers content and prevents lines/cards from stretching too wide. */
main {
  padding: 1rem;
  max-width: 1100px;
  margin: 0 auto;
}

/* AI COMMENT: Shared spacing below major blocks keeps the page visually organized. */
.controls,
.statistics,
.courses-grid,
.add-course {
  margin-bottom: 1rem;
}

/* AI COMMENT: Common card-like visual styling reused by controls, stats, form panel, and course cards. */
.controls,
.add-course,
.stat-item,
.course-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  box-shadow: var(--shadow);
}

/* AI COMMENT: Inner padding gives controls room so fields/buttons are easy to scan and tap. */
.controls {
  padding: 1rem;
}

/* AI COMMENT: Search/filter/action rows use flex-wrap so controls remain usable on narrow screens. */
.search-section,
.filter-section,
.action-section {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-bottom: 0.5rem;
}

/* AI COMMENT: Inherit same font across form controls and buttons for a consistent UI. */
input,
select,
textarea,
button {
  font: inherit;
}

/* AI COMMENT: Default input/select/textarea appearance with visible borders and comfortable touch size. */
input,
select,
textarea {
  width: 100%;
  padding: 0.6rem 0.7rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #fff;
}

/* AI COMMENT: Primary button style used for all actions to keep interactions obvious. */
button {
  border: 1px solid transparent;
  border-radius: 8px;
  padding: 0.6rem 0.9rem;
  cursor: pointer;
  background: var(--primary);
  color: #fff;
}

/* AI COMMENT: Hover state gives visual feedback when pointer users interact with buttons. */
button:hover {
  background: var(--primary-hover);
}

/* AI COMMENT: Disabled state communicates temporary unavailability and prevents misleading clicks. */
button:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

/* AI CHANGE: Explicit focus-visible styling for keyboard users */
/* AI COMMENT: Visible high-contrast focus states are a WCAG baseline for keyboard accessibility. */
:focus-visible {
  outline: 3px solid #f59e0b;
  outline-offset: 2px;
}

/* AI COMMENT: Feedback box styles show operation status (success/error/info) after user actions. */
.feedback {
  padding: 0.75rem;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: #f9fafb;
}

/* AI COMMENT: Success message colors indicate successful operations such as load/add/export. */
.feedback.success {
  background: var(--ok-bg);
  color: var(--ok-text);
  border-color: #86efac;
}

/* AI COMMENT: Error message colors indicate validation or parsing failures users must fix. */
.feedback.error {
  background: var(--danger-bg);
  color: var(--danger-text);
  border-color: #fca5a5;
}

/* AI COMMENT: Informational messages show non-error status updates like current result count. */
.feedback.info {
  background: #dbeafe;
  color: #1e3a8a;
  border-color: #93c5fd;
}

/* AI COMMENT: Utility class toggles visibility for modal, form panel, and message containers. */
.hidden {
  display: none !important;
}

/* AI COMMENT: Stats cards use a responsive 3-column grid on wider screens. */
.statistics {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.75rem;
}

/* AI COMMENT: Individual statistic cards center numeric values and labels for quick scanning. */
.stat-item {
  padding: 0.9rem;
  text-align: center;
}

/* AI COMMENT: Larger bold number emphasizes key metrics like totals and percentages. */
.stat-number {
  display: block;
  font-size: 1.5rem;
  font-weight: 700;
}

/* AI COMMENT: Muted label tone keeps focus on the numeric stat while preserving context text. */
.stat-label {
  color: var(--muted);
}

/* AI CHANGE: Responsive course grid (1 to 3 columns) */
/* AI COMMENT: Meets assignment requirement for responsive card layout and keeps rendering efficient when many cards are present. */
.courses-grid {
  min-height: 120px;
  padding: 0.25rem;
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.8rem;
}

/* AI COMMENT: Each course card has internal padding to separate content blocks clearly. */
.course-card {
  padding: 0.9rem;
}

/* AI COMMENT: Card header aligns course code and credit count on one line. */
.course-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.5rem;
}

/* AI COMMENT: Removes default heading margin so custom spacing can be controlled consistently. */
.course-code {
  margin: 0;
}

/* AI COMMENT: Title margin sets readable separation between header and details. */
.course-title {
  margin: 0.4rem 0;
}

/* AI COMMENT: Shared vertical rhythm for text metadata blocks in course cards. */
.course-description,
.instructor-info,
.schedule-info,
.enrollment-info {
  margin: 0.45rem 0;
}

/* AI COMMENT: Topics wrap into pill tags so long lists stay readable within card width. */
.topics {
  display: flex;
  gap: 0.35rem;
  flex-wrap: wrap;
  margin-top: 0.5rem;
}

/* AI COMMENT: Topic tag style visually groups related keywords without overpowering core details. */
.topic-tag {
  display: inline-block;
  padding: 0.2rem 0.45rem;
  border-radius: 999px;
  border: 1px solid #bfdbfe;
  background: #eff6ff;
  color: #1e3a8a;
  font-size: 0.85rem;
}

/* AI COMMENT: Green status means enrollment level is open/healthy. */
.enrollment-info.open {
  background: var(--ok-bg);
  color: var(--ok-text);
  padding: 0.45rem;
  border-radius: 8px;
}

/* AI COMMENT: Yellow status warns the class is filling up. */
.enrollment-info.filling {
  background: var(--warn-bg);
  color: var(--warn-text);
  padding: 0.45rem;
  border-radius: 8px;
}

/* AI COMMENT: Red status indicates a near-full or full class. */
.enrollment-info.full {
  background: var(--danger-bg);
  color: var(--danger-text);
  padding: 0.45rem;
  border-radius: 8px;
}

/* AI COMMENT: Loading and empty-result messages use a neutral container to stand out from cards. */
.loading,
.no-results {
  padding: 1rem;
  text-align: center;
  background: #fff;
  border: 1px dashed var(--border);
  border-radius: 8px;
}

/* AI COMMENT: Add-course panel matches card style so form feels integrated with the rest of the UI. */
.add-course {
  padding: 1rem;
}

/* AI COMMENT: Removes default top margin from section heading to align with panel padding. */
.add-course h2 {
  margin-top: 0;
}

/* AI COMMENT: Form grid arranges inputs in two columns for desktop and tablet efficiency. */
.form-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.75rem;
}

/* AI COMMENT: Label text is emphasized so beginners can quickly map fields to required data. */
.form-grid label {
  display: block;
  font-weight: 600;
  font-size: 0.95rem;
}

/* AI COMMENT: Small top spacing separates label text from the related input control. */
.form-grid input,
.form-grid select,
.form-grid textarea {
  margin-top: 0.3rem;
}

/* AI COMMENT: Full-width utility lets larger text fields span both columns when needed. */
.full-width {
  grid-column: 1 / -1;
}

/* AI COMMENT: Form action buttons are grouped for a clear submit/cancel workflow. */
.form-actions {
  margin-top: 0.75rem;
  display: flex;
  gap: 0.5rem;
}

/* AI COMMENT: Form error box highlights validation issues returned from JavaScript checks. */
.form-errors {
  margin-top: 0.75rem;
  padding: 0.75rem;
  border-radius: 8px;
  border: 1px solid #fca5a5;
  background: var(--danger-bg);
  color: var(--danger-text);
}

/* AI CHANGE: Modal visual and keyboard-friendly close behavior support */
/* AI COMMENT: Modal uses full-screen overlay, clear contrast, and a focusable content container for accessibility. */
.modal {
  position: fixed;
  inset: 0;
  background: rgba(17, 24, 39, 0.65);
  display: grid;
  place-items: center;
  padding: 1rem;
  z-index: 1000;
}

/* AI COMMENT: Modal content container limits width/height and scrolls if details are long. */
.modal-content {
  width: min(720px, 100%);
  max-height: 90vh;
  overflow: auto;
  background: #fff;
  border-radius: 10px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
  padding: 1rem;
  position: relative;
}

/* AI COMMENT: Close button is anchored in the corner for predictable keyboard and mouse access. */
.close-btn {
  position: absolute;
  top: 0.5rem;
  right: 0.5rem;
  font-size: 1.4rem;
  line-height: 1;
  width: 2rem;
  height: 2rem;
  border-radius: 50%;
  padding: 0;
}

/* AI COMMENT: Screen-reader-only helper keeps labels accessible while visually hidden. */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* AI COMMENT: Medium screens switch courses grid from one to two columns. */
@media (min-width: 700px) {
  .courses-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

/* AI COMMENT: Large screens use three columns for better space usage and browsing speed. */
@media (min-width: 1024px) {
  .courses-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

/* AI COMMENT: Mobile layout stacks stats/form fields and ensures controls meet touch target size guidance. */
@media (max-width: 680px) {
  .statistics {
    grid-template-columns: 1fr;
  }

  .form-grid {
    grid-template-columns: 1fr;
  }

  button,
  input,
  select,
  textarea {
    min-height: 44px;
  }
}