Alien Ruin fix, various cherrypicked upstream fixes

Also adds new buildmode

code/modules/buildmode/README.md

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+# Buildmode
+
+## Code layout
+
+### Buildmode
+
+Manager for buildmode modes. Contains logic to manage switching between each mode, and presenting a suitable user interface.
+
+### Effects
+
+Special graphics used by buildmode modes for user interface purposes.
+
+### Buildmode Mode
+
+Implementer of buildmode behaviors.
+
+Existing varieties:
+
++ Basic
+
+	**Description**:
+
+	Allows creation of simple structures consisting of floors, walls, windows, and airlocks.
+
+	**Controls**:
+
+	+ *Left click a turf*:
+	
+		"Upgrades" the turf based on the following rules below:
+
+		+ Space -> Tiled floor
+		+ Simulated floor -> Regular wall
+		+ Wall -> Reinforced wall
+	
+	+ *Right click a turf*:
+
+		"Downgrades" the turf based on the following rules below:
+
+		+ Reinforced wall -> Regular wall
+		+ Wall -> Tiled floor
+		+ Simulated floor -> Space
+	
+	+ *Right click an object*:
+
+		Deletes the clicked object.
+
+	+ *Alt+Left click a location*:
+
+		Places an airlock at the clicked location.
+	
+	+ *Ctrl+Left click a location*:
+
+		Places a window at the clicked location.
+
++ Advanced
+
+	**Description**:
+
+	Creates an instance of a configurable atom path where you click.
+
+	**Controls**:
+
+	+ *Right click on the mode selector*:
+
+		Choose a path to spawn.
+	
+	+ *Left click a location* (requires chosen path):
+
+		Place an instance of the chosen path at the location.
+
+	+ *Right click an object*:
+
+		Delete the object.
+
++ Fill
+
+	**Description**:
+
+	Creates an instance of an atom path on every tile in a chosen region.
+
+	With a special control input, instead deletes everything within the region.
+
+	**Controls**:
+
+	+ *Right click on the mode selector*:
+
+		Choose a path to spawn.
+
+	+ *Left click on a region* (requires chosen path):
+
+		Fill the region with the chosen path.
+
+	+ *Alt+Left click on a region*:
+
+		Deletes everything within the region.
+
+	+ *Right click during region selection*:
+
+		Cancel region selection.
+
++ Copy
+
+	**Description**:
+	
+	Take an existing object in the world, and place duplicates with identical attributes where you click.
+
+	May not always work nicely - "deep" variables such as lists or datums may malfunction.
+
+	**Controls**:
+
+	+ *Right click an existing object*:
+
+		Select the clicked object as a template.
+
+	+ *Left click a location* (Requires a selected object as template):
+
+		Place a duplicate of the template at the clicked location.
+
++ Area Edit
+
+	**Description**:
+
+	Modifies and creates areas.
+
+	The active area will be highlighted in yellow.
+
+	**Controls**:
+
+	+ *Right click the mode selector*:
+
+		Create a new area, and make it active.
+
+	+ *Right click an existing area*:
+
+		Make the clicked area active.
+
+	+ *Left click a turf*:
+
+		When an area is active, adds the turf to the active area.
+
++ Var Edit
+
+	**Description**:
+
+	Allows for setting and resetting variables of objects with a click.
+
+	If the object does not have the var, will do nothing and print a warning message.
+
+	**Controls**:
+
+	+ *Right click the mode selector*:
+
+		Choose which variable to set, and what to set it to.
+
+	+ *Left click an atom*:
+
+		Change the clicked atom's variables as configured.
+	
+	+ *Right click an atom*:
+
+		Reset the targeted variable to its original value in the code.
+
++ Map Generator
+
+	**Description**:
+
+	Fills rectangular regions with algorithmically generated content. Right click during region selection to cancel.
+
+	See the `procedural_mapping` module for the generators themselves.
+
+	**Controls**:
+
+	+ *Right-click on the mode selector*:
+	
+		Select a map generator from all the generators present in the codebase.
+		
+	+ *Left click two corners of an area*:
+
+		Use the generator to populate the region.
+
+	+ *Right click during region selection*:
+
+		Cancel region selection.
+
++ Throwing
+
+	**Description**:
+
+	Select an object with left click, and right click to throw it towards where you clicked.
+
+	**Controls**:
+
+	+ *Left click on a movable atom*:
+		
+		Select the atom for throwing.
+	
+	+ *Right click on a location*:
+
+		Throw the selected atom towards that location.
+
++ Boom
+
+	**Description**:
+
+	Make explosions where you click.
+
+	**Controls**:
+
+	+ *Right click the mode selector*:
+	
+		Configure the explosion size.
+
+	+ *Left click a location*:
+	
+		Cause an explosion where you clicked.