Almost working from 1st try

mechanism.lua

@@ -0,0 +1,69 @@
+require 'tablefuncs'
+require 'gridpoint'
+require 'port'
+
+---@param xcorner GridPoint
+---@param size GridPoint
+---@return GridPoint
+local function nextxcorner( xcorner, size )
+    local cornerLookup = {
+        GridPoint:new( 0, 0 ),
+        GridPoint:new( size.x - 1, 0 ),
+        GridPoint:new( size.x - 1, size.y - 1 ),
+        GridPoint:new( size.x - 1, size.y - 1 )
+    }
+    local index = TableFind(cornerLookup, xcorner, function(value) value:equals(xcorner) end)
+    if index < #cornerLookup then
+        index = index + 1
+    else
+        index = 0
+    end
+    return cornerLookup[index]
+end
+
+---@class Mechanism
+---@field position GridPoint
+---@field size GridPoint
+---@field xcorner GridPoint
+---@field ports Port[]
+---@field color table
+Mechanism = {
+    position = GridPoint:new( 0, 0 ),
+    size = GridPoint:new( 1, 1 ),
+    xcorner = GridPoint:new( 0, 0 ),
+    ports = {},
+    color = { 0.5, 0.5, 0.5, 1 }
+}
+
+function Mechanism:new( position, size, ports, color )
+    local mechanism = {
+        position = position or self.position,
+        size = size or self.size,
+        ports = ports or {},
+        color = color or self.color
+    }
+
+    setmetatable( mechanism, { __index = self } )
+
+    return mechanism
+end
+
+function Mechanism:rotateClockwise()
+    self.xcorner = nextxcorner(self.xcorner, self.size)
+    for _, port in ipairs(self.ports) do
+        port:rotateClockwise()
+    end
+end
+
+function Mechanism:draw()
+    love.graphics.setColor(self.color)
+    local x, y = self.position:globalCoords()
+    x = x - Config.cellSize / 2
+    y = y - Config.cellSize / 2
+    local w, h = self.size:globalCoords()
+    love.graphics.rectangle("fill", x, y, w, h)
+    for _, port in ipairs(self.ports) do
+        local offset = GridPoint:new( self.position.x + self.xcorner.x, self.position.y + self.xcorner.y )
+        port:draw( offset )
+    end
+end