/* styles/main.css
   Design tokens, CSS reset, and base typography for StudyBuddy.
   Visual language: clean blue-accented "study desk" UI — white surfaces,
   soft gray backgrounds, a confident primary blue, and calm status colors. */

:root {
  /* ---- Color tokens ---- */
  --color-bg: #F7F8FB;
  --color-surface: #FFFFFF;
  --color-border: #E6E8F0;
  --color-border-strong: #D7DAE6;

  --color-text: #14182B;
  --color-text-muted: #5B6172;
  --color-text-faint: #9499A8;

  --color-primary: #2F5FE0;
  --color-primary-dark: #2347B8;
  --color-primary-light: #EAF0FE;
  --color-primary-tint: #DCE6FD;

  --color-success: #2F9E5C;
  --color-success-dark: #267F4A;
  --color-success-light: #E6F6EC;

  --color-amber: #D98C20;
  --color-amber-light: #FCF1DE;

  --color-rose: #E0526F;
  --color-rose-light: #FCE8EC;

  --color-violet: #6E56CF;
  --color-violet-light: #EDE9FB;

  --color-green: #2F9E5C;
  --color-green-light: #E6F6EC;

  --color-slate: #5B6172;
  --color-slate-light: #EEF0F4;

  --color-blue: #2F5FE0;
  --color-blue-light: #EAF0FE;

  --color-danger: #D64545;
  --color-danger-light: #FBEAEA;

  /* ---- Typography ---- */
  --font-base: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --font-mono: "JetBrains Mono", "SF Mono", Consolas, monospace;

  /* ---- Layout ---- */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-full: 999px;

  --shadow-sm: 0 1px 2px rgba(20, 24, 43, 0.04);
  --shadow-md: 0 4px 16px rgba(20, 24, 43, 0.06);
  --shadow-lg: 0 12px 32px rgba(20, 24, 43, 0.10);

  --sidebar-width: 240px;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
}

body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  font-family: var(--font-base);
  background: var(--color-bg);
  color: var(--color-text);
  font-size: 15px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

#app-root {
  flex: 1;
}

h1, h2, h3, h4, p, ul, ol {
  margin: 0;
}

ul, ol {
  padding: 0;
  list-style: none;
}

button {
  font-family: inherit;
  cursor: pointer;
}

a {
  color: inherit;
  text-decoration: none;
}

img {
  max-width: 100%;
  display: block;
}

#app-root {
  min-height: 100vh;
}

.screen {
  min-height: 100vh;
}

.wave {
  display: inline-block;
}

/* ---- Generic helpers ---- */
.empty-state {
  color: var(--color-text-faint);
  font-size: 14px;
  padding: 24px 0;
}

.fatal-error {
  max-width: 480px;
  margin: 80px auto;
  text-align: center;
  padding: 32px;
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
}

.fatal-error h2 {
  margin-bottom: 12px;
}

.fatal-error p {
  color: var(--color-text-muted);
}

/* ---- Buttons ---- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  font-family: inherit;
  font-size: 14px;
  font-weight: 600;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  padding: 10px 18px;
  transition: background 0.15s ease, transform 0.05s ease, border-color 0.15s ease;
  white-space: nowrap;
}

.btn:active {
  transform: scale(0.98);
}

.btn:disabled {
  opacity: 0.55;
  cursor: not-allowed;
  transform: none;
}

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

.btn--success {
  background: var(--color-success);
  color: #fff;
}
.btn--success:hover:not(:disabled) {
  background: var(--color-success-dark);
}

.btn--outline {
  background: var(--color-surface);
  border-color: var(--color-border-strong);
  color: var(--color-text);
}
.btn--outline:hover:not(:disabled) {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.btn--text {
  background: transparent;
  color: var(--color-primary);
  padding: 8px 0;
}
.btn--text:hover:not(:disabled) {
  color: var(--color-primary-dark);
}

.btn--sm {
  padding: 6px 14px;
  font-size: 13px;
}

.btn--full {
  width: 100%;
}

/* ---- Badges ---- */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 12px;
  font-weight: 600;
  padding: 4px 9px;
  border-radius: var(--radius-full);
  white-space: nowrap;
}

.badge--success {
  background: var(--color-success-light);
  color: var(--color-success-dark);
}

/* ---- Icon button ---- */
.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-full);
  border: 1px solid var(--color-border);
  background: var(--color-surface);
  color: var(--color-text-muted);
}
.icon-btn:hover {
  background: var(--color-bg);
  color: var(--color-text);
}

/* ---- Toasts ---- */
.toast-container {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 1000;
  pointer-events: none;
}

.toast {
  background: var(--color-text);
  color: #fff;
  padding: 12px 20px;
  border-radius: var(--radius-md);
  font-size: 14px;
  font-weight: 500;
  box-shadow: var(--shadow-lg);
  opacity: 0;
  transform: translateY(8px);
  transition: opacity 0.2s ease, transform 0.2s ease;
}

.toast--visible {
  opacity: 1;
  transform: translateY(0);
}

.toast--error {
  background: var(--color-danger);
}

.toast--success {
  background: var(--color-success-dark);
}

/* ---- Modal (notes viewer) ---- */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(20, 24, 43, 0.45);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 900;
  padding: 20px;
}

.modal {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  max-width: 520px;
  width: 100%;
  max-height: 80vh;
  overflow-y: auto;
  box-shadow: var(--shadow-lg);
}

.modal__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px 20px;
  border-bottom: 1px solid var(--color-border);
}

.modal__header h3 {
  font-size: 17px;
  font-weight: 700;
}

.modal__header .icon-btn svg {
  transform: rotate(180deg);
}

.modal__body {
  padding: 20px;
  color: var(--color-text-muted);
  line-height: 1.7;
  font-size: 14.5px;
}