local from = arena:getCell(pos)

			arena:setCell(pos, Cell{owner=self.owner})

			arena:setCell(pos, from)

		arena:setCell(pos + dirFromString(direction), Cell{owner=self.owner, core=fun, energy=self.energy * energy})

		local oldEnergy = self.energy
		local cell = Cell{owner=self.owner, core=fun, energy=self.energy * energy}
		arena:setCell(pos + dirFromString(direction), cell, function()
			self.energy = oldEnergy
		end)

		-- TODO: more checks

		-- TODO: more checks and return value

	send = function(self, pos, arena, data, direction)

	send = function(_, pos, arena, data, direction)

	inspect = function(self, pos, arena, direction)

	inspect = function(_, pos, arena, direction)

	wait = function(self, amount)
		-- TODO: check amount

	wait = function(_, amount)
		-- TODO: check amount, use world ticks

		cell.cell = cell.original

		cell.cells = {cell.original}

		table.insert(self.cells[x][y].actions, undo)

		if undo then
			table.insert(self.cells[x][y].actions, undo)
		end

	function Arena:draw()
		for y = 1, height do
			for _ = 1, width*7 do
				io.write("-")
			end
			io.write("\n|")
			for x = 1, width do
				local owner = self:getCell(Vector(x, y)).owner
				io.write(string.format("%-5s", tostring(owner):sub(5)))
				io.write("|")
			end
			io.write("\n")
			for _ = 1, width*7 do
				io.write("-")
			end
			io.write("\n")
		end
	end