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

:root {
  --sidebar-width: 200px;
  --header-height: 56px;
  --bg-dark: #1e1e2e;
  --bg-sidebar: #2a2a3e;
  --bg-section: #32324a;
  --border: #44445a;
  --text: #e0e0f0;
  --text-muted: #888;
  --accent: #6c63ff;
  --accent-hover: #7d75ff;
  --cell-size: 24px;
  --grout-color: #555;
  --grout-size: 2px;
}

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: var(--bg-dark);
  color: var(--text);
  height: 100vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

/* ── Header ──────────────────────────────────────────── */
.app-header {
  height: var(--header-height);
  background: var(--bg-sidebar);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1rem;
  flex-shrink: 0;
  gap: 1rem;
}

.app-header h1 {
  font-size: 1.1rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  color: var(--text);
  white-space: nowrap;
}

.header-actions {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}

#file-input {
  display: none;
}

/* ── Buttons ─────────────────────────────────────────── */
button {
  cursor: pointer;
  border: none;
  border-radius: 6px;
  font-size: 0.8rem;
  font-weight: 600;
  padding: 0.35rem 0.75rem;
  transition: background 0.15s, opacity 0.15s;
}

.btn-primary {
  background: var(--accent);
  color: #fff;
}
.btn-primary:hover {
  background: var(--accent-hover);
}

.btn-secondary {
  background: var(--bg-section);
  color: var(--text);
  border: 1px solid var(--border);
  width: 100%;
  margin-top: 0.4rem;
}
.btn-secondary:hover {
  background: var(--border);
}

.btn-danger {
  background: #c0392b;
  color: #fff;
  border: 1px solid #922b21;
  width: 100%;
  margin-top: 0.4rem;
}
.btn-danger:hover {
  background: #a93226;
}

.btn-icon {
  background: var(--bg-section);
  color: var(--text);
  border: 1px solid var(--border);
}
.btn-icon:hover:not(:disabled) {
  background: var(--border);
}
.btn-icon:disabled {
  opacity: 0.35;
  cursor: not-allowed;
}

/* ── Layout ──────────────────────────────────────────── */
.app-body {
  display: flex;
  flex: 1;
  overflow: hidden;
}

/* ── Sidebar ─────────────────────────────────────────── */
.sidebar {
  width: var(--sidebar-width);
  background: var(--bg-sidebar);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  flex-shrink: 0;
  padding: 0.5rem;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.sidebar-section {
  background: var(--bg-section);
  border-radius: 8px;
  padding: 0.6rem 0.7rem;
}

.sidebar-section h3 {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: 0.5rem;
}

/* ── Tool Buttons ────────────────────────────────────── */
.tools {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.tool-btn {
  background: var(--bg-sidebar);
  color: var(--text);
  border: 1px solid var(--border);
  text-align: left;
  padding: 0.4rem 0.6rem;
  border-radius: 6px;
  font-size: 0.8rem;
}
.tool-btn:hover {
  background: var(--border);
}
.tool-btn.active {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

/* ── Grid Size Inputs ────────────────────────────────── */
.grid-inputs {
  display: flex;
  gap: 0.4rem;
  margin-bottom: 0.2rem;
}

.grid-inputs label {
  display: flex;
  align-items: center;
  gap: 0.25rem;
  font-size: 0.8rem;
  flex: 1;
}

.grid-inputs input {
  width: 100%;
  background: var(--bg-sidebar);
  border: 1px solid var(--border);
  color: var(--text);
  border-radius: 5px;
  padding: 0.25rem 0.3rem;
  font-size: 0.8rem;
  text-align: center;
}
.grid-inputs input:focus {
  outline: 1px solid var(--accent);
}

/* ── Palette ─────────────────────────────────────────── */
.palette {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 4px;
}

.palette-swatch {
  width: 100%;
  aspect-ratio: 1;
  border-radius: 4px;
  border: 2px solid transparent;
  cursor: pointer;
  transition: transform 0.1s, border-color 0.1s;
  padding: 0;
}
.palette-swatch:hover {
  transform: scale(1.15);
}
.palette-swatch.active {
  border-color: #fff;
  transform: scale(1.1);
  box-shadow: 0 0 0 2px var(--accent);
}

/* ── Replace ─────────────────────────────────────────── */
.replace-row {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  margin-bottom: 0.2rem;
}

.replace-picker-btn {
  width: 36px;
  height: 36px;
  border-radius: 6px;
  border: 2px solid var(--border);
  padding: 0;
  flex-shrink: 0;
  cursor: pointer;
  transition: border-color 0.15s;
}
.replace-picker-btn:hover {
  border-color: #fff;
}

.replace-arrow {
  font-size: 1.1rem;
  color: var(--text-muted);
  flex: 1;
  text-align: center;
}

/* ── Replace popup ───────────────────────────────────── */
.replace-picker-popup {
  position: fixed;
  background: var(--bg-sidebar);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px;
  display: grid;
  grid-template-columns: repeat(4, 28px);
  gap: 5px;
  z-index: 999;
  box-shadow: 0 6px 24px rgba(0,0,0,0.5);
}
.replace-picker-popup.hidden {
  display: none;
}

.replace-picker-popup .picker-swatch {
  width: 28px;
  height: 28px;
  border-radius: 4px;
  border: 2px solid transparent;
  cursor: pointer;
  padding: 0;
  transition: transform 0.1s;
}
.replace-picker-popup .picker-swatch:hover {
  transform: scale(1.2);
  border-color: #fff;
}

/* ── Counters ────────────────────────────────────────── */
#counters {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
}

.counter-item {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.78rem;
}

.counter-swatch {
  width: 16px;
  height: 16px;
  border-radius: 3px;
  flex-shrink: 0;
  border: 1px solid rgba(255,255,255,0.15);
}

.counter-name {
  flex: 1;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  color: var(--text);
}

.counter-count {
  font-weight: 700;
  font-size: 0.85rem;
  color: var(--accent);
  min-width: 2ch;
  text-align: right;
}

.counter-empty {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-style: italic;
}

/* ── Grid Area ───────────────────────────────────────── */
.grid-area {
  flex: 1;
  overflow: auto;
  padding: 1.5rem;
  background: #13131f;
  display: flex;
  align-items: flex-start;
  justify-content: flex-start;
}

/* ── Grid ────────────────────────────────────────────── */
.grid {
  display: grid;
  gap: var(--grout-size);
  background: var(--grout-color);
  border: var(--grout-size) solid var(--grout-color);
  border-radius: 2px;
  cursor: crosshair;
  user-select: none;
  -webkit-user-select: none;
  touch-action: none;
}

.grid.tool-fill {
  cursor: cell;
}
.grid.tool-eraser {
  cursor: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='20' height='20' viewBox='0 0 20 20'%3E%3Crect x='2' y='2' width='16' height='16' rx='2' fill='none' stroke='%23fff' stroke-width='2'/%3E%3C/svg%3E") 10 10, crosshair;
}

/* ── Cells ───────────────────────────────────────────── */
.cell {
  width: var(--cell-size);
  height: var(--cell-size);
  transition: filter 0.05s;
}

.cell:hover {
  filter: brightness(1.25);
}

.cell.empty {
  background-color: #fff;
  background-image:
    linear-gradient(45deg, #ccc 25%, transparent 25%),
    linear-gradient(-45deg, #ccc 25%, transparent 25%),
    linear-gradient(45deg, transparent 75%, #ccc 75%),
    linear-gradient(-45deg, transparent 75%, #ccc 75%);
  background-size: 8px 8px;
  background-position: 0 0, 0 4px, 4px -4px, -4px 0;
}

/* ── Scrollbar ───────────────────────────────────────── */
.sidebar::-webkit-scrollbar,
.grid-area::-webkit-scrollbar {
  width: 6px;
  height: 6px;
}
.sidebar::-webkit-scrollbar-track,
.grid-area::-webkit-scrollbar-track {
  background: transparent;
}
.sidebar::-webkit-scrollbar-thumb,
.grid-area::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 3px;
}