Almost working from 1st try

mouse.lua

@@ -0,0 +1,19 @@
+-- TODO: rewrite
+---@class Mouse
+---@field x integer
+---@field y integer
+---@field point GridPoint
+Mouse = {
+    x = 0,
+    y = 0,
+    point = GridPoint:new( 0, 0 )
+}
+
+-- TODO: fix collision with other line's endpoint
+function Mouse:update()
+    Mouse.x, Mouse.y = love.mouse.getPosition()
+    Mouse.x = Mouse.x + 1
+    Mouse.y = Mouse.y + 1
+
+    Mouse.point = GridPoint.snapCoords( Point:new( Mouse.x, Mouse.y ) )
+end