function collide_side(self)

	local offset=self.w/3
	for i=-(self.w/3),(self.w/3),2 do
	--if self.dx>0 then
		if fget(mget((self.x+(offset))/8,(self.y+i)/8),0) then
			self.dx=0
			self.x=(flr(((self.x+(offset))/8))*8)-(offset)
			return true
		end
	--elseif self.dx<0 then
		if fget(mget((self.x-(offset))/8,(self.y+i)/8),0) then
			self.dx=0
			self.x=(flr((self.x-(offset))/8)*8)+8+(offset)
			return true
		end
--	end
	end
	--didn't hit a solid tile.
	return false
end

-- Check for collision on the sides of "self", and shift "self" back
-- to the edge of the wall in the case that they do hit something.
function collide_side(self)

	-- This function works by checking a few points along the right and left edge of the 
	-- object (self). It starts at the top and works down to the bottom.

	-- Usually you might check for collision at the edge of the object (which would be
	-- an offset of width/2), but the sprite doesn't take up the whole width of the 
	-- object, so instead offset by a 3rd, giving a little bit of overlap with the walls.
	local offset=self.w/3

	-- This loop will check collision every 2 pixels from top to bottom of the object, both on the 
	-- left and right edge.
	-- 'i' will be the vertical position, while the x offset is fixed ("offset").
	for i=-(self.w/3),(self.w/3),2 do

		-- a lot happens here so I'll try to explain it in chunks...
		-- self.x+(offset): move to the right edge of the object.strokeWidth
		-- (self.x+(offset))/8: divide by 8 (the width of a tile) to put this into "map space".
		-- (self.y+i)/8): check a position on the edge, from top to bottom. Again, put it into "map space".
		-- mget(...): get the tile id that this point is inside of.
		-- fget(..., 0): Check if flag 0 is set on the tile, which means "solid" for this engine.
		if fget(mget((self.x+(offset))/8,(self.y+i)/8),0) then
			-- A collision has been detected...
			-- Stop the horizontal momentum (dx, and dy represent velocity).
			self.dx=0
			-- self.x+(offset))/8: Get the x position of the tile we hit in map space.
			-- flr(...): truncate it down to ensure that it is an actual tile number.
			-- ... * 8: now put it back into world space, but because it was truncated before, this will put it on the left edge of the tile.
			self.x=(flr(((self.x+(offset))/8))*8)-(offset)
			-- A collision was found, no need to continue...
			return true
		end

		-- This is the same as above, but checking the left edge instead.
		if fget(mget((self.x-(offset))/8,(self.y+i)/8),0) then
			self.dx=0
			-- Same as above, but because we are check the left edge of the object, we want to butt it
			-- against the right edge of the tile, so there is an extra +8.
			self.x=(flr((self.x-(offset))/8)*8)+8+(offset)
			return true
		end
	end
	--didn't hit a solid tile.
	return false
end