Rework fallSystem for modifiable gravity.

Add receivedInputThisFrame bool to InputState

src/systems/filter-types.lua

@@ -9,7 +9,7 @@
 ---@alias Collision { collisionBetween: Entity[] }
 ---@alias Entity table
 ---@alias InRelations Entity[]
----@alias InputState { aJustPressed: boolean, bJustPressed: boolean, upJustPressed: boolean, downJustPressed: boolean, leftJustPressed: boolean, rightJustPressed: boolean }
+---@alias InputState { receivedInputThisFrame: boolean, aJustPressed: boolean, bJustPressed: boolean, upJustPressed: boolean, downJustPressed: boolean, leftJustPressed: boolean, rightJustPressed: boolean }
 ---@alias RoundStateAction "end" | "start"
 ---@alias XyPair { x: number, y: number }
 

src/systems/filter-types.lua2p

@@ -61,7 +61,7 @@ end
     CanSpawn = "{ entity: Entity }",
     InRelations = "Entity[]",
     CanBeBounced = "{ flat: XyPair, mult = XyPair }",
-    InputState = "{ aJustPressed: boolean, bJustPressed: boolean, upJustPressed: boolean, downJustPressed: boolean, leftJustPressed: boolean, rightJustPressed: boolean }",
+    InputState = "{ receivedInputThisFrame: boolean, aJustPressed: boolean, bJustPressed: boolean, upJustPressed: boolean, downJustPressed: boolean, leftJustPressed: boolean, rightJustPressed: boolean }",
 }))
 
 T = {

src/systems/gravity.lua

@@ -1,4 +1,15 @@
-local G = -300
-fallSystem = filteredSystem("fall", { velocity = T.XyPair, mass = T.number }, function(e, dt)
-    e.velocity.y = e.velocity.y - (G * dt * e.mass) - (0.5 * dt * dt)
+world:addEntity({ gravity = -300 })
+
+gravities = filteredSystem("gravities", { gravity = T.number })
+
+filteredSystem("changeGravity", { changeGravityTo = T.number }, function(e, _, _)
+    for _, ge in pairs(gravities.entities) do
+        ge.gravity = e.changeGravityTo
+    end
+end)
+
+fallSystem = filteredSystem("fall", { velocity = T.XyPair, mass = T.number }, function(e, dt)
+    for _, ge in pairs(gravities.entities) do
+        e.velocity.y = e.velocity.y - (ge.gravity * dt * e.mass) - (0.5 * dt * dt)
+    end
 end)

src/systems/input.lua

@@ -1,6 +1,6 @@
----@alias InputState { upJustPressed: boolean, downJustPressed: boolean, rightJustPressed: boolean, leftJustPressed: boolean, aJustPressed: boolean, bJustPressed: boolean }
-
 local buttonJustPressed = playdate.buttonJustPressed
+
+---@type InputState
 local inputState = {}
 
 inputSystem = filteredSystem("input", { canReceiveInput = T.marker }, function(e, _, system)
@@ -15,4 +15,12 @@ function inputSystem:preProcess()
     inputState.leftJustPressed = buttonJustPressed(playdate.kButtonLeft)
     inputState.aJustPressed = buttonJustPressed(playdate.kButtonA)
     inputState.bJustPressed = buttonJustPressed(playdate.kButtonB)
+
+    inputState.receivedInputThisFrame =
+        inputState.upJustPressed
+        or inputState.downJustPressed
+        or inputState.rightJustPressed
+        or inputState.leftJustPressed
+        or inputState.aJustPressed
+        or inputState.bJustPressed
 end

src/systems/menu.lua

@@ -4,20 +4,26 @@
 local MenuItems = {}
 
 menuController = filteredSystem("menuController", { menuItems = MenuItems, inputState = T.InputState }, function(e, _, system)
+    if not e.inputState.receivedInputThisFrame then
+        return
+    end
+
     for _, menuItem in pairs(e.menuItems) do
         if menuItem.highlighted then
             if e.inputState.aJustPressed then
-                menuItem.onSelect(system.world)
+                menuItem.onSelect(system.world) -- TODO: That's not very ECS of you!
                 for _, item in pairs(e.menuItems) do
                     system.world:removeEntity(item)
                 end
                 system.world:removeEntity(e)
             end
+
             if e.inputState.downJustPressed and menuItem.navigateDown then
                 menuItem.highlighted = false
                 menuItem.navigateDown.highlighted = true
                 return
             end
+
             if e.inputState.upJustPressed and menuItem.navigateUp then
                 menuItem.highlighted = false
                 menuItem.navigateUp.highlighted = true
@@ -25,6 +31,7 @@ menuController = filteredSystem("menuController", { menuItems = MenuItems, input
             end
         end
     end
+
     for _, menuItem in pairs(e.menuItems) do
         if menuItem.highlighted then
             menuItem.drawAsText.style = TextStyle.Inverted