:root {
  color-scheme: light;
  --bg: #f4f7fb;
  --panel: #ffffff;
  --grid: #d8e0ec;
  --header: #eef3f9;
  --header-strong: #dce6f4;
  --text: #17324d;
  --muted: #67809b;
  --active: #2563eb;
  --range: rgba(37, 99, 235, 0.12);
  --focus: rgba(37, 99, 235, 0.18);
  --shadow: 0 16px 40px rgba(15, 23, 42, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background: linear-gradient(180deg, #f8fbff 0%, var(--bg) 100%);
  color: var(--text);
  font: 14px/1.4 Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

.app-shell {
  display: grid;
  grid-template-rows: auto 1fr;
  gap: 16px;
  min-height: 100vh;
  padding: 16px;
}

.formula-bar-shell,
.grid-shell {
  background: var(--panel);
  border: 1px solid rgba(148, 163, 184, 0.24);
  border-radius: 16px;
  box-shadow: var(--shadow);
}

.formula-bar-shell {
  display: grid;
  grid-template-columns: 88px 1fr;
  gap: 12px;
  align-items: center;
  padding: 12px;
}

.name-box {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 40px;
  border-radius: 10px;
  background: var(--header);
  color: var(--text);
  font-weight: 600;
}

.formula-input {
  min-width: 0;
  min-height: 40px;
  border: 1px solid var(--grid);
  border-radius: 10px;
  padding: 0 12px;
  font: inherit;
  color: inherit;
  outline: none;
}

.formula-input:focus {
  border-color: var(--active);
  box-shadow: 0 0 0 4px var(--focus);
}

.grid-shell {
  overflow: auto;
  padding: 12px;
}

.sheet {
  border-collapse: separate;
  border-spacing: 0;
  min-width: max-content;
}

.sheet th,
.sheet td {
  border-right: 1px solid var(--grid);
  border-bottom: 1px solid var(--grid);
}

.sheet thead th {
  position: sticky;
  top: 0;
  z-index: 2;
  background: var(--header);
}

.sheet th.corner,
.sheet tbody th {
  position: sticky;
  left: 0;
  z-index: 1;
  background: var(--header);
}

.sheet th.corner {
  z-index: 3;
}

.sheet th {
  min-width: 56px;
  height: 36px;
  padding: 0 8px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 700;
  text-align: center;
}

.sheet td {
  position: relative;
  min-width: 108px;
  width: 108px;
  height: 32px;
  padding: 0;
  background: #fff;
}

.cell-button,
.cell-editor {
  width: 100%;
  height: 100%;
  border: 0;
  padding: 0 10px;
  background: transparent;
  color: inherit;
  font: inherit;
  text-align: left;
  outline: none;
}

.cell-button {
  cursor: cell;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.cell.in-range {
  background: var(--range);
}

.cell.active {
  box-shadow: inset 0 0 0 2px var(--active);
  background: #fff;
}

.sheet .header-active {
  background: var(--header-strong);
  color: var(--text);
}

@media (max-width: 720px) {
  .app-shell {
    padding: 10px;
    gap: 10px;
  }

  .formula-bar-shell {
    grid-template-columns: 72px 1fr;
    gap: 8px;
    padding: 10px;
  }

  .sheet td {
    min-width: 92px;
    width: 92px;
  }
}