Preview adjacent rooms during transitions

world.lua

@@ -796,6 +796,8 @@ function World:nextRoom(room, pos)
 	elseif pos.y > gridHeight then exit, entry.y = "bottom", 1
 	elseif pos.y < 1 then exit, entry.y = "top", gridHeight end
 	local nextName = self:getNeighbor(room.name, exit) or room.name
+	local sourceLocation = self:roomLocation(room.name)
+	local destinationLocation = self:roomLocation(nextName)
 	local activeColors = room:getActiveColors()
 	self:markDirty(room)
 	local destination = self.levels[nextName]
@@ -817,6 +819,13 @@ function World:nextRoom(room, pos)
 	end
 	room.activeColors = {red = false, green = false, blue = false}
 	currentRoom = destination
+	if sourceLocation and destinationLocation and nextName ~= room.name then
+		self.roomTransition = {
+			startedAt = love.timer.getTime(), duration = 0.28,
+			dx = destinationLocation.x - sourceLocation.x,
+			dy = destinationLocation.y - sourceLocation.y,
+		}
+	end
 	self:markDirty(currentRoom)
 	for _, color in ipairs(activeColors) do
 		currentRoom.player[color].x, currentRoom.player[color].y = entry.x, entry.y
@@ -884,6 +893,48 @@ function World:drawOverlaps(room, color)
 	end
 end
 
+-- Render the active room at a small zoom-out, together with the eight world
+-- neighbours around it.  This is display-only: individual rooms still own
+-- their data, collision, and authored boundary walls.
+function World:drawRoomNeighborhood(room)
+	if self.drawingRoomNeighborhood then return end
+	local location = self:roomLocation(room.name)
+	if not location then return end
+
+	-- Leave enough margin to read several cells of each neighbour, not merely
+	-- its boundary wall.  This keeps a nearby separated player discoverable.
+	local zoom = 0.78
+	local originX = (width - width * zoom) / 2
+	local originY = (height - height * zoom) / 2
+	local cameraX, cameraY = 0, 0
+	local transition = self.roomTransition
+	if transition then
+		local progress = math.min(1, (love.timer.getTime() - transition.startedAt) / transition.duration)
+		-- Smoothstep keeps the scene anchored at both ends instead of snapping
+		-- into or out of its small neighbourhood preview.
+		local eased = progress * progress * (3 - 2 * progress)
+		cameraX = transition.dx * (1 - eased)
+		cameraY = transition.dy * (1 - eased)
+		if progress >= 1 then self.roomTransition = nil end
+	end
+	self.drawingRoomNeighborhood = true
+	for roomY = -1, 1 do
+		for roomX = -1, 1 do
+			local name = self:roomAt(location.x + roomX, location.y + roomY)
+			local adjacent = name and self.levels[name]
+			if adjacent then
+				love.graphics.push()
+				love.graphics.translate(originX + (roomX + cameraX) * width * zoom,
+					originY + (roomY + cameraY) * height * zoom)
+				love.graphics.scale(zoom, zoom)
+				adjacent:draw()
+				love.graphics.pop()
+			end
+		end
+	end
+	self.drawingRoomNeighborhood = false
+end
+
 function World:getCellFromMousePos(mouseX, mouseY)
 	return math.floor(mouseX / (width / self.width)) + 1, math.floor(mouseY / (height / self.height)) + 1
 end