*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg: #ffffff;
  --surface: #f8f9fa;
  --border: #d0d7de;
  --border-strong: #b0b7bf;
  --accent: #3b5bdb;
  --accent-light: #e7ecfd;
  --selected-bg: #cce8ff;
  --selected-border: #2196f3;
  --header-bg: #f0f2f5;
  --header-text: #444;
  --row-even: #fafafa;
  --formula-bg: #fff;
  --error: #c0392b;
  --formula-color: #154360;
  --text: #1a1a1a;
  --status: #666;
}

html, body { height: 100%; overflow: hidden; font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif; font-size: 13px; color: var(--text); background: var(--bg); }

/* Layout */
#app { display: flex; flex-direction: column; height: 100vh; }

/* Toolbar */
#toolbar {
  display: flex; align-items: center; gap: 8px;
  padding: 6px 10px;
  background: var(--accent);
  color: #fff;
  flex-shrink: 0;
}
#toolbar h1 { font-size: 14px; font-weight: 600; letter-spacing: 0.3px; margin-right: auto; }
#logout-btn {
  background: rgba(255,255,255,0.15); border: none; color: #fff;
  padding: 3px 10px; border-radius: 3px; cursor: pointer; font-size: 12px;
}
#logout-btn:hover { background: rgba(255,255,255,0.25); }

/* Formula bar */
#formula-row {
  display: flex; align-items: center; gap: 0;
  border-bottom: 1px solid var(--border);
  background: var(--formula-bg);
  flex-shrink: 0;
}
#cell-ref-box {
  width: 72px; min-width: 72px;
  padding: 5px 8px;
  border-right: 1px solid var(--border);
  font-size: 12px; color: var(--header-text);
  font-family: monospace;
  text-align: center;
}
#formula-bar {
  flex: 1; border: none; outline: none;
  padding: 5px 10px;
  font-size: 13px; font-family: monospace;
  background: transparent;
  color: var(--text);
}
#fx-label {
  padding: 0 8px; color: var(--accent); font-style: italic;
  font-size: 13px; font-weight: 500; user-select: none;
  border-right: 1px solid var(--border);
}

/* Grid wrapper */
#grid-wrapper {
  flex: 1; overflow: auto;
  position: relative;
}

/* Table */
#grid {
  border-collapse: collapse;
  table-layout: fixed;
  width: max-content;
}

#grid th, #grid .corner, #grid .rownum {
  background: var(--header-bg);
  color: var(--header-text);
  font-weight: 500;
  text-align: center;
  user-select: none;
}

#grid th {
  position: sticky; top: 0; z-index: 2;
  padding: 3px 0;
  border: 1px solid var(--border);
  min-width: 80px; width: 80px;
  font-size: 12px;
}

#grid .corner {
  position: sticky; top: 0; left: 0; z-index: 3;
  width: 42px; min-width: 42px;
  border: 1px solid var(--border);
}

#grid .rownum {
  position: sticky; left: 0; z-index: 1;
  width: 42px; min-width: 42px;
  padding: 0 4px;
  border: 1px solid var(--border);
  font-size: 11px;
  color: #888;
}

#grid td {
  border: 1px solid var(--border);
  padding: 2px 5px;
  height: 22px; min-height: 22px;
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
  outline: none;
  cursor: default;
  min-width: 80px; width: 80px;
  vertical-align: middle;
}

#grid tbody tr:nth-child(even) td:not(.rownum) { background: var(--row-even); }

#grid td.selected {
  background: var(--selected-bg) !important;
  outline: 2px solid var(--selected-border);
  outline-offset: -2px;
  z-index: 1; position: relative;
}

#grid td.editing {
  background: #fff !important;
  outline: 2px solid var(--accent) !important;
  outline-offset: -2px;
  overflow: visible;
  white-space: pre;
  z-index: 2; position: relative;
  cursor: text;
}

#grid td.formula { color: var(--formula-color); }
#grid td.error { color: var(--error); font-style: italic; }

/* Column header highlight when selected */
#grid th.col-active { background: var(--selected-bg); color: #000; }
#grid .rownum.row-active { background: var(--selected-bg); color: #000; }

/* Sheet tabs */
#sheets-bar {
  display: flex; align-items: stretch;
  background: var(--header-bg);
  border-top: 1px solid var(--border);
  height: 28px; flex-shrink: 0;
}
#sheets-tabs { display: flex; overflow-x: auto; flex: 1; }
#sheets-tabs::-webkit-scrollbar { height: 3px; }
#sheets-tabs::-webkit-scrollbar-thumb { background: var(--border-strong); }

.sheet-tab {
  padding: 0 14px; cursor: pointer;
  border-right: 1px solid var(--border);
  white-space: nowrap; display: flex; align-items: center;
  font-size: 12px; user-select: none; color: var(--header-text);
}
.sheet-tab:hover { background: #e8eaed; }
.sheet-tab.active {
  background: #fff; font-weight: 600; color: var(--accent);
  border-top: 2px solid var(--accent);
}
.tab-rename {
  border: none; outline: 1px solid var(--accent);
  font-size: 12px; font-weight: 600; color: var(--accent);
  background: #fff; width: 80px; padding: 0 2px;
}
#add-sheet-btn {
  padding: 0 12px; background: none; border: none; border-left: 1px solid var(--border);
  cursor: pointer; font-size: 18px; color: #888; line-height: 1;
}
#add-sheet-btn:hover { background: #e8eaed; color: var(--accent); }

/* Status bar */
#status-bar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 2px 10px;
  border-top: 1px solid var(--border);
  background: var(--surface);
  flex-shrink: 0;
  font-size: 11px; color: var(--status);
}
#status { font-size: 11px; }

/* Scrollbar */
#grid-wrapper::-webkit-scrollbar { width: 8px; height: 8px; }
#grid-wrapper::-webkit-scrollbar-track { background: var(--surface); }
#grid-wrapper::-webkit-scrollbar-thumb { background: var(--border-strong); border-radius: 4px; }

/* Login page */
.login-page {
  display: flex; align-items: center; justify-content: center;
  height: 100vh; background: var(--surface);
}
.login-card {
  background: #fff; border: 1px solid var(--border);
  border-radius: 8px; padding: 40px 36px;
  width: 320px; box-shadow: 0 2px 12px rgba(0,0,0,0.07);
  text-align: center;
}
.login-card h1 { font-size: 20px; color: var(--accent); margin-bottom: 4px; }
.login-card p { color: var(--status); font-size: 13px; margin-bottom: 24px; }
.login-card input[type=password] {
  width: 100%; padding: 9px 12px; font-size: 14px;
  border: 1px solid var(--border); border-radius: 4px; outline: none;
  margin-bottom: 12px;
}
.login-card input[type=password]:focus { border-color: var(--accent); }
.login-card button {
  width: 100%; padding: 9px; font-size: 14px;
  background: var(--accent); color: #fff; border: none;
  border-radius: 4px; cursor: pointer; font-weight: 500;
}
.login-card button:hover { background: #1a5c38; }
.login-card .error-msg { color: var(--error); font-size: 12px; margin-top: 8px; min-height: 18px; }