Preview adjacent rooms during transitions

room.lua

@@ -131,6 +131,10 @@ function Room:update(dt)
 end
 
 function Room:draw()
+	if gameWorld and gameWorld.levels and gameWorld.levels[self.name] == self and
+		not gameWorld.drawingRoomNeighborhood then
+		return gameWorld:drawRoomNeighborhood(self)
+	end
 	self:drawWiresAt(0, 0, width / gridWidth, nil, false)
 
 	-- draw only the channels the player has. Each object just exposes sprites per
@@ -139,7 +143,13 @@ function Room:draw()
 	for _, channel in ipairs(self.colorsPlayerHas) do
 		if self.player[channel] then self.player[channel]:draw(channel) end
 		for _, entity in pairs(self.collideables[channel]) do entity:draw(channel) end
-		if gameWorld and gameWorld.levels and gameWorld.levels[self.name] == self then gameWorld:drawOverlaps(self, channel) end
+		-- The zoomed-out neighbourhood already draws every room directly. Calling
+		-- the legacy seam helper from each miniature room duplicates foreign
+		-- entities, which can screen-blend red and green into a false yellow.
+		if gameWorld and gameWorld.levels and gameWorld.levels[self.name] == self and
+			not gameWorld.drawingRoomNeighborhood then
+			gameWorld:drawOverlaps(self, channel)
+		end
 		for _, blocker in pairs(self.playerBlockers[channel]) do blocker:draw(channel) end
 		for _, switch in pairs(self.switches[channel]) do switch:draw(channel) end
 		for _, switch in ipairs(self.wiredSwitches) do switch:draw(channel) end

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