Map cache

A mock of the real-map streaming + caching algorithm (no API yet). Move the cursor over the field — it is the player. Each coloured square is a fetched map covering a region; cached maps are drawn faint, the active one solid. The dashed inner square is the active map's safe zone; the dashed circle is the player's vision. A new map is needed the moment vision would reach past the active map's edge — reusing a cached map when one has enough buffer, otherwise fetching (and caching) a new one centred on the player.