:root {
  --bg: #0e1510;
  --surface: #18201a;
  --surface-2: #232f26;
  --text: #ecf1ec;
  --muted: #9db09f;
  --primary: #78BC61;
  --primary-press: #5fa049;
  --border: #2e3d33;
  --again: #ef4444;
  --hard: #f59e0b;
  --good: #22c55e;
  --easy: #38bdf8;
  --radius: 16px;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #eef6ea;
    --surface: #ffffff;
    --surface-2: #e5f1df;
    --text: #1b2c1e;
    --muted: #63735f;
    --border: #dbe8d3;
  }
}

* { box-sizing: border-box; }

/* The `hidden` attribute must win over element display rules like flex/grid below,
   otherwise hidden answers/buttons still render. */
[hidden] { display: none !important; }

html, body {
  margin: 0;
  height: 100%;
  /* The rubber-band / overscroll region exposes the html background, so paint it
     with the app background (not the brand green) to keep pulls from feeling jarring. */
  background: var(--bg);
}

body {
  color: var(--text);
  font: 16px/1.5 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  -webkit-tap-highlight-color: transparent;
  /* Suppress the browser's own pull-to-refresh; app.js provides a custom one. */
  overscroll-behavior-y: contain;
}

/* Page content. app.js slides this down (transform) during a pull-to-refresh,
   revealing the spinner in the gap above it. */
#app {
  display: flex;
  flex-direction: column;
  min-height: 100dvh;
  transition: transform 0.2s ease;
}

/* Pull-to-refresh indicator: parked just above the viewport, slid down by app.js. */
.ptr {
  position: fixed;
  top: env(safe-area-inset-top, 0px);
  left: 0;
  right: 0;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  transform: translateY(-44px);
  opacity: 0;
  z-index: 20; /* above the sticky topbar */
  pointer-events: none;
  transition: transform 0.2s ease, opacity 0.2s ease;
}
.ptr-spinner {
  width: 26px;
  height: 26px;
  border-radius: 50%;
  border: 3px solid var(--border);
  border-top-color: var(--primary);
}
.ptr.refreshing .ptr-spinner {
  animation: ptr-spin 0.8s linear infinite;
}
@keyframes ptr-spin { to { transform: rotate(360deg); } }

/* Top bar */
.topbar {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 16px calc(14px + env(safe-area-inset-top));
  padding-top: max(14px, env(safe-area-inset-top));
  border-bottom: 1px solid var(--border);
  background: var(--surface);
  position: sticky;
  top: 0;
  z-index: 10;
}

.brand {
  margin: 0;
  display: flex;
  align-items: center;
  line-height: 0;
  color: var(--text);
}

.brand-logo {
  height: 36px;
  width: auto;
  display: block;
}

.tabs {
  display: flex;
  gap: 4px;
  margin-left: auto;
  background: var(--surface-2);
  padding: 4px;
  border-radius: 999px;
}

.tab {
  border: 0;
  background: transparent;
  color: var(--muted);
  font: inherit;
  font-weight: 600;
  padding: 6px 16px;
  border-radius: 999px;
  cursor: pointer;
}

.tab[aria-current="true"] {
  background: var(--primary);
  color: #fff;
}

.sync {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--muted);
  flex: none;
}
.sync.online { background: var(--good); }
.sync.offline { background: var(--hard); }
.sync.syncing { background: var(--easy); animation: pulse 1s infinite; }
@keyframes pulse { 50% { opacity: 0.3; } }

main {
  flex: 1;
  width: 100%;
  max-width: 640px;
  margin: 0 auto;
  padding: 20px 16px calc(24px + env(safe-area-inset-bottom));
}

.view { display: block; }
.view[hidden] { display: none; }

.muted { color: var(--muted); font-size: 14px; }

/* Buttons */
.btn {
  font: inherit;
  font-weight: 600;
  border: 1px solid var(--border);
  background: var(--surface-2);
  color: var(--text);
  padding: 12px 16px;
  border-radius: 12px;
  cursor: pointer;
  transition: transform 0.05s ease, filter 0.1s ease;
}
.btn:active { transform: translateY(1px); }
.btn-primary {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}
.btn-primary:hover { background: var(--primary-press); }
.btn-wide { width: 100%; }

/* Study mode toggle (Due / All) */
.study-modes {
  display: flex;
  gap: 4px;
  background: var(--surface-2);
  padding: 4px;
  border-radius: 999px;
  width: fit-content;
  margin: 0 auto 24px; /* breathing room above the card */
}
.mode-btn {
  border: 0;
  background: transparent;
  color: var(--muted);
  font: inherit;
  font-weight: 600;
  padding: 6px 20px;
  border-radius: 999px;
  cursor: pointer;
}
.mode-btn[aria-current="true"] {
  background: var(--primary);
  color: #fff;
}

/* Study card */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px 20px;
  min-height: 320px;
  display: flex;
  flex-direction: column;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.12);
}

.card-progress {
  color: var(--muted);
  font-size: 13px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 16px;
}

.card-face {
  font-size: 24px;
  font-weight: 600;
  text-align: center;
  padding: 20px 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex: 1;
  word-break: break-word;
  /* Keep intentional line breaks from multi-line cards while still wrapping. */
  white-space: pre-wrap;
}

.card-back {
  border-top: 1px dashed var(--border);
  color: var(--primary);
}

.card-actions { margin-top: auto; }

.grades {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
}
.grades .grade { padding: 14px 4px; }
.grade[data-grade="again"] { border-color: var(--again); color: var(--again); }
.grade[data-grade="hard"] { border-color: var(--hard); color: var(--hard); }
.grade[data-grade="good"] { border-color: var(--good); color: var(--good); }
.grade[data-grade="easy"] { border-color: var(--easy); color: var(--easy); }

/* Empty state */
.empty {
  text-align: center;
  padding: 60px 20px;
  color: var(--muted);
}
.empty p { margin: 4px 0; }

/* Manage view */
/* Front and back are stacked (each on its own row) so they can be roomy textareas. */
.add-form {
  display: grid;
  gap: 8px;
  margin-bottom: 24px;
}

.input {
  font: inherit;
  padding: 12px 14px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  width: 100%;
}
.input:focus {
  outline: 2px solid var(--primary);
  border-color: var(--primary);
}
/* Multi-line front/back entry. */
textarea.input {
  resize: vertical;
  min-height: 3.2em;
  line-height: 1.4;
}

.card-list {
  list-style: none;
  margin: 12px 0 0;
  padding: 0;
  display: grid;
  gap: 8px;
}

.card-item {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px 14px;
  display: flex;
  align-items: center;
  gap: 12px;
}
.card-item .texts { flex: 1; min-width: 0; }
.card-item .front { font-weight: 600; }
.card-item .back { color: var(--muted); font-size: 14px; }
.card-item .front, .card-item .back {
  /* Wrap long cards instead of forcing a horizontal scroll on mobile. */
  white-space: pre-wrap;
  overflow-wrap: anywhere;
}
.card-item .due {
  font-size: 12px;
  color: var(--muted);
  flex: none;
}

.icon-btn {
  border: 0;
  background: transparent;
  color: var(--muted);
  cursor: pointer;
  font-size: 18px;
  padding: 6px;
  border-radius: 8px;
  flex: none;
}
.icon-btn:hover { background: var(--surface-2); }
.icon-btn.delete:hover, .icon-btn.cancel:hover { color: var(--again); }
.icon-btn.edit:hover { color: var(--primary); }
.icon-btn.save:hover { color: var(--good); }

/* Inline edit fields in a manage row */
.edit-fields {
  display: grid;
  gap: 6px;
}
.edit-fields .input {
  padding: 8px 10px;
  font-size: 15px;
}