A placed tilemap grows and shrinks at every edge: the new GRID EDGES block in the inspector adds or removes one column or row at Left, Top, Right or Bottom as one undo step, shifting the cells of all layers and moving the placement through its own matrix so the content stays in place on screen; removed painted cells are kept outside the grid and return when the edge grows again, and the Columns and Rows fields of a placement keep the content in place too (#136)

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/core/properties/PropertySchema.ts

@@ -21,7 +21,7 @@ import {
 } from './kinds';
 import { findAssetOf, type Project } from '../model/Project';
 import { TILE_FPS_KEY, TILE_KIND_KEY, TILE_PLAYBACK_KEY, TILE_SOLID_KEY } from '../model/tile';
-import { TILEMAP_COLUMNS_KEY, TILEMAP_ROWS_KEY, TILEMAP_TILE_KEY } from '../model/tilemap';
+import { TILEMAP_COLUMNS_KEY, TILEMAP_MAX_CELLS, TILEMAP_ROWS_KEY, TILEMAP_TILE_KEY } from '../model/tilemap';
 import { SLICE_SCALE_KEY } from '../model/texture';
 import type { SceneObject } from '../model/SceneObject';
 import { flatListOf, listItemOf } from './listItems';
@@ -254,8 +254,24 @@ const ASSET_SCHEMAS: Record<AssetType, PropertySchema> = {
   // how far the grid reaches and how big one cell is drawn. A tile's own pictures are scaled onto
   // that cell, so one tilemap can mix tiles drawn at different resolutions.
   tilemap: [
-    { key: TILEMAP_COLUMNS_KEY, label: 'Columns', kind: 'number', default: 20, min: 1, max: 1000, step: 1 },
-    { key: TILEMAP_ROWS_KEY, label: 'Rows', kind: 'number', default: 15, min: 1, max: 1000, step: 1 },
+    {
+      key: TILEMAP_COLUMNS_KEY,
+      label: 'Columns',
+      kind: 'number',
+      default: 20,
+      min: 1,
+      max: TILEMAP_MAX_CELLS,
+      step: 1,
+    },
+    {
+      key: TILEMAP_ROWS_KEY,
+      label: 'Rows',
+      kind: 'number',
+      default: 15,
+      min: 1,
+      max: TILEMAP_MAX_CELLS,
+      step: 1,
+    },
     { key: TILEMAP_TILE_KEY, label: 'Tile size', kind: 'number', default: 48, min: 1, step: 1 },
   ],
   // Behaviors declare their own properties (variables) per asset too – see `schemaForAsset`.