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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Malgun Gothic', sans-serif;
  background: #f0f2f5;
  color: #1a1a2e;
  height: 100vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

/* ─── Header ─────────────────────────────── */
header {
  background: #1e293b;
  color: white;
  padding: 12px 24px;
  display: flex;
  align-items: center;
  gap: 20px;
  flex-shrink: 0;
  min-height: 52px;
}

header h1 {
  font-size: 17px;
  font-weight: 700;
  white-space: nowrap;
}

.summary {
  display: flex;
  gap: 8px;
}
.summary.hidden { display: none; }

.summary-item {
  font-size: 12px;
  padding: 3px 10px;
  border-radius: 12px;
  font-weight: 600;
  white-space: nowrap;
}
.summary-item.modified { background: #fef08a; color: #713f12; }
.summary-item.added    { background: #bbf7d0; color: #14532d; }
.summary-item.deleted  { background: #fecaca; color: #7f1d1d; }

.header-hint {
  font-size: 12px;
  color: #94a3b8;
  white-space: nowrap;
}
.header-hint.hidden { display: none; }

/* ─── Panels ─────────────────────────────── */
.panels {
  display: flex;
  flex: 1;
  overflow: hidden;
}

.panel {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  background: white;
  min-width: 0;
}

.splitter {
  width: 5px;
  background: #e2e8f0;
  flex-shrink: 0;
  cursor: col-resize;
}

.panel-header {
  display: flex;
  align-items: center;
  padding: 9px 16px;
  background: #f8fafc;
  border-bottom: 1px solid #e2e8f0;
  flex-shrink: 0;
  min-height: 42px;
}

.panel-title {
  font-size: 13px;
  font-weight: 600;
  color: #475569;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

/* ─── Drop Zone ──────────────────────────── */
.drop-zone {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 2px dashed #cbd5e1;
  margin: 20px;
  border-radius: 12px;
  cursor: pointer;
  transition: all 0.2s;
  background: #f8fafc;
}

.drop-zone:hover,
.drop-zone.drag-over {
  border-color: #6366f1;
  background: #eef2ff;
}

.drop-zone.hidden { display: none; }

.drop-content {
  text-align: center;
  color: #64748b;
  pointer-events: none;
}

.drop-content label {
  pointer-events: all;
}

.drop-icon {
  font-size: 44px;
  margin-bottom: 12px;
  line-height: 1;
}

.drop-content p {
  font-size: 14px;
  margin-bottom: 12px;
}

.file-hint {
  font-size: 12px !important;
  color: #94a3b8;
  margin-top: 8px !important;
  margin-bottom: 0 !important;
}

.btn-upload {
  display: inline-block;
  background: #6366f1;
  color: white;
  padding: 8px 20px;
  border-radius: 6px;
  font-size: 13px;
  cursor: pointer;
  transition: background 0.2s;
}
.btn-upload:hover { background: #4f46e5; }

/* ─── Sheet Tabs ─────────────────────────── */
.sheet-tabs {
  display: flex;
  gap: 4px;
  padding: 8px 12px;
  background: #f1f5f9;
  border-bottom: 1px solid #e2e8f0;
  flex-shrink: 0;
  overflow-x: auto;
}
.sheet-tabs.hidden { display: none; }

.sheet-tab {
  padding: 3px 12px;
  border: 1px solid #cbd5e1;
  border-radius: 4px;
  background: white;
  font-size: 12px;
  cursor: pointer;
  white-space: nowrap;
  transition: all 0.15s;
  color: #475569;
}
.sheet-tab.active {
  background: #6366f1;
  color: white;
  border-color: #6366f1;
}
.sheet-tab:hover:not(.active) { background: #e0e7ff; }

/* ─── Table ──────────────────────────────── */
.table-container {
  flex: 1;
  overflow: auto;
}
.table-container.hidden { display: none; }

table {
  border-collapse: collapse;
  font-size: 12px;
  width: max-content;
  min-width: 100%;
}

td {
  padding: 5px 10px;
  border: 1px solid #e2e8f0;
  white-space: nowrap;
  max-width: 220px;
  overflow: hidden;
  text-overflow: ellipsis;
  vertical-align: middle;
}

tr:nth-child(even) td { background: #f8fafc; }

/* ─── Diff Styles ────────────────────────── */
.cell-modified {
  background: #fef9c3 !important;
  cursor: pointer;
  position: relative;
}
.cell-modified:hover {
  background: #fde047 !important;
  outline: 2px solid #ca8a04;
  outline-offset: -2px;
  z-index: 1;
}
.cell-modified::after {
  content: '✎';
  position: absolute;
  right: 3px;
  top: 2px;
  font-size: 9px;
  color: #92400e;
  opacity: 0.6;
}

.cell-added   { background: #dcfce7 !important; }
.cell-deleted { background: #fee2e2 !important; }

.row-placeholder td { background: #f1f5f9 !important; border-color: #e2e8f0 !important; }
.row-added    td { background: #dcfce7 !important; }
.row-deleted  td { background: #fee2e2 !important; }

/* ─── Footer / Download ──────────────────── */
.panel-footer {
  padding: 10px 16px;
  border-top: 1px solid #e2e8f0;
  background: #f8fafc;
  flex-shrink: 0;
}
.panel-footer.hidden { display: none; }

.btn-download {
  background: #059669;
  color: white;
  border: none;
  padding: 8px 16px;
  border-radius: 6px;
  font-size: 13px;
  cursor: pointer;
  width: 100%;
  transition: background 0.2s;
  font-family: inherit;
}
.btn-download:hover { background: #047857; }

/* ─── Context Menu ───────────────────────── */
.context-menu {
  position: fixed;
  background: white;
  border: 1px solid #e2e8f0;
  border-radius: 8px;
  box-shadow: 0 4px 20px rgba(0,0,0,0.15);
  z-index: 1000;
  overflow: hidden;
  min-width: 160px;
}
.context-menu.hidden { display: none; }

.context-menu div {
  padding: 10px 16px;
  font-size: 13px;
  cursor: pointer;
  transition: background 0.15s;
}
.context-menu div:hover { background: #f1f5f9; }