/* ============================================================
   Bảng Học Lớp 1 — giao diện
   Phong cách: sáng, vui tươi, thân thiện với bé; khoảng rộng
   ============================================================ */
:root {
  --bg:        #f2f8f4;
  --surface:   #ffffff;
  --line:      #e3ebe5;
  --ink:       #1f3128;
  --ink-2:     #5c6f65;
  --ink-3:     #8b9a91;

  --green:     #2fae5f;   /* chữ cái */
  --green-d:   #1f8c48;
  --green-l:   #e5f7ec;
  --orange:    #f5911e;   /* số */
  --orange-l:  #fff2e0;
  --blue:      #2f6bff;   /* tập viết */
  --blue-l:    #e7efff;
  --danger:    #e5484d;

  --font: "Nunito", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --r-md: 14px;
  --r-lg: 20px;
  --shadow-sm: 0 1px 2px rgba(31,49,40,.05), 0 4px 14px rgba(31,49,40,.06);
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html, body { height: 100%; }
body {
  font-family: var(--font);
  color: var(--ink);
  background: var(--bg);
  display: flex; flex-direction: column;
  overflow: hidden;
  -webkit-font-smoothing: antialiased;
}

/* ---------- Thanh trên ---------- */
.bar {
  flex-shrink: 0;
  display: flex; align-items: center; gap: 12px;
  background: var(--surface);
  border-bottom: 1px solid var(--line);
  padding: 10px 14px;
  box-shadow: 0 1px 4px rgba(31,49,40,.05);
  z-index: 20;
}
.back {
  flex-shrink: 0;
  display: inline-flex; align-items: center; gap: 6px;
  font-family: var(--font); font-size: 14px; font-weight: 800;
  color: var(--ink-2); background: #f0f4f1;
  border: none; border-radius: 999px;
  padding: 9px 14px 9px 11px; cursor: pointer;
  transition: color .15s, background .15s;
}
.back:hover { color: var(--green-d); background: var(--green-l); }
.back:active { transform: scale(.97); }

.bar__title {
  font-size: clamp(1.05rem, 2.6vw, 1.35rem);
  font-weight: 900; letter-spacing: -.01em;
  color: var(--green-d);
  white-space: nowrap;
}

.tabs { margin-left: auto; display: flex; gap: 6px; background: #eef3ef; padding: 5px; border-radius: 999px; }
.tab {
  font-family: var(--font); font-size: 14px; font-weight: 800;
  color: var(--ink-2); background: transparent;
  border: none; border-radius: 999px;
  padding: 9px 18px; cursor: pointer;
  transition: background .15s, color .15s;
  white-space: nowrap;
}
.tab:hover { color: var(--ink); }
.tab.is-on { background: var(--green); color: #fff; box-shadow: 0 3px 10px rgba(47,174,95,.35); }

/* ---------- Vùng nội dung ---------- */
.stage { flex: 1; min-height: 0; overflow: hidden; display: flex; }
.panel { flex: 1; min-width: 0; display: none; flex-direction: column; overflow: hidden; }
.panel.is-on { display: flex; }
.panel[hidden] { display: none; }

.panel__head {
  flex-shrink: 0;
  display: flex; align-items: center; justify-content: space-between; gap: 12px;
  padding: 16px 20px 8px;
}
.panel__heading { font-size: 1.1rem; font-weight: 900; color: var(--ink); }
.pill {
  font-family: var(--font); font-size: 13.5px; font-weight: 800;
  color: #fff; background: var(--green);
  border: none; border-radius: 999px;
  padding: 9px 16px; cursor: pointer;
  box-shadow: 0 3px 10px rgba(47,174,95,.32);
  transition: background .15s, transform .05s;
}
.pill:hover { background: var(--green-d); }
.pill:active { transform: translateY(1px); }

.grid { flex: 1; overflow-y: auto; padding: 8px 20px 24px; align-content: start; }

/* Thẻ chữ cái */
.grid--letters {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(130px, 1fr));
  gap: 14px;
}
.lcard {
  background: var(--surface);
  border: 2px solid var(--green-l);
  border-top: 5px solid var(--green);
  border-radius: var(--r-lg);
  padding: 16px 12px;
  text-align: center;
  box-shadow: var(--shadow-sm);
  transition: transform .15s, box-shadow .15s;
}
.lcard:hover { transform: translateY(-4px); box-shadow: 0 8px 22px rgba(31,49,40,.1); }
.lcard__upper { font-size: 2.6rem; font-weight: 900; color: var(--green-d); line-height: 1; }
.lcard__img { width: 46px; height: 46px; object-fit: contain; margin: 8px auto 6px; display: block; }
.lcard__ex { font-size: .95rem; font-weight: 700; color: var(--ink-2); }

/* Thẻ số */
.grid--numbers {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: 16px;
  max-width: 1000px; margin: 0 auto;
}
.ncard {
  background: var(--surface);
  border: 2px solid var(--orange-l);
  border-top: 5px solid var(--orange);
  border-radius: var(--r-lg);
  padding: 20px 16px;
  text-align: center;
  box-shadow: var(--shadow-sm);
  transition: transform .15s;
}
.ncard:hover { transform: translateY(-4px); }
.ncard__num { font-size: 3.4rem; font-weight: 900; color: var(--orange); line-height: 1; }
.ncard__dots { font-size: 1.1rem; color: var(--blue); margin: 10px 0 8px; min-height: 20px; letter-spacing: 2px; word-break: break-word; }
.ncard__word { font-size: 1.05rem; font-weight: 800; color: var(--ink-2); }

/* ---------- Tập viết ---------- */
.panel--writing { padding: 12px 16px 16px; }
.tools {
  flex-shrink: 0;
  display: flex; align-items: center; gap: 8px;
  flex-wrap: wrap;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 7px 10px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 12px;
}
.tools__grp { display: inline-flex; align-items: center; gap: 4px; padding-right: 8px; border-right: 1px solid var(--line); }
.tools__grp:last-child { border-right: none; padding-right: 0; }
.tools__grp--size { gap: 8px; }

.tbtn {
  display: inline-grid; place-items: center;
  width: 40px; height: 40px;
  border: none; border-radius: 50%;
  background: #f0f4f1; color: var(--ink-2);
  cursor: pointer; transition: background .15s, color .15s, transform .05s;
}
.tbtn:hover { background: var(--blue-l); color: var(--blue); }
.tbtn:active { transform: scale(.92); }
.tbtn.is-on { background: var(--blue); color: #fff; }
.tbtn--danger:hover { background: #fdecec; color: var(--danger); }

.swatch { display: inline-grid; place-items: center; width: 40px; height: 40px; border-radius: 50%; cursor: pointer; }
.swatch input[type="color"] { width: 30px; height: 30px; border: none; border-radius: 50%; padding: 0; background: none; cursor: pointer; }
.swatch input[type="color"]::-webkit-color-swatch-wrapper { padding: 0; }
.swatch input[type="color"]::-webkit-color-swatch { border: 2px solid #fff; border-radius: 50%; box-shadow: 0 0 0 1px var(--line); }

.colors { display: inline-flex; gap: 4px; }
.dot { width: 22px; height: 22px; border-radius: 50%; border: 2px solid #fff; box-shadow: 0 0 0 1px var(--line); cursor: pointer; transition: transform .1s; }
.dot:hover { transform: scale(1.15); }
.dot.is-on { box-shadow: 0 0 0 2px var(--blue); }

#size { width: 96px; accent-color: var(--blue); cursor: pointer; }
.size-val { font-size: 13px; font-weight: 800; color: var(--ink-2); min-width: 22px; text-align: center; font-variant-numeric: tabular-nums; }

.paper {
  flex: 1; min-height: 0;
  position: relative;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  /* Nền ô ly như vở tập viết */
  background-image:
    linear-gradient(to right, #eef2f7 1px, transparent 1px),
    linear-gradient(to bottom, #eef2f7 1px, transparent 1px),
    linear-gradient(to bottom, #d5e0f0 1px, transparent 1px);
  background-size: 32px 32px, 32px 32px, 100% 128px;
}
#board { position: absolute; inset: 0; width: 100%; height: 100%; display: block; cursor: crosshair; touch-action: none; }

/* ---------- Popup ---------- */
.popup {
  position: fixed; inset: 0;
  background: rgba(15,25,20,.55);
  display: flex; align-items: center; justify-content: center;
  padding: 20px; z-index: 100;
}
.popup[hidden] { display: none; }
.popup__box { position: relative; max-width: 900px; max-height: 88vh; }
.popup__box img { max-width: 100%; max-height: 88vh; border-radius: 12px; box-shadow: 0 12px 40px rgba(0,0,0,.35); display: block; }
.popup__close {
  position: absolute; top: -14px; right: -14px;
  width: 40px; height: 40px; border-radius: 50%;
  background: #fff; color: var(--ink); border: none;
  display: grid; place-items: center; cursor: pointer;
  box-shadow: 0 4px 14px rgba(0,0,0,.25);
}
.popup__close:hover { color: var(--danger); }

/* ---------- Responsive ---------- */
@media (max-width: 720px) {
  .bar { flex-wrap: wrap; gap: 8px; padding: 8px 12px; }
  .bar__title { order: -1; }
  .back__txt { display: none; }
  .tabs { margin-left: 0; width: 100%; justify-content: center; }
  .tab { flex: 1; padding: 9px 8px; }
  .grid { padding: 8px 12px 20px; }
  .grid--letters { grid-template-columns: repeat(auto-fill, minmax(100px, 1fr)); gap: 10px; }
  .lcard__upper { font-size: 2rem; }
  .lcard__img { width: 38px; height: 38px; }
  .panel--writing { padding: 10px; }
  .tools { border-radius: 16px; }
}

@media (prefers-reduced-motion: reduce) {
  .lcard, .ncard, .tab, .tbtn, .back, .dot { transition: none; }
}