Brought in screen manager, minor refactor.

screens/scene.go

@@ -0,0 +1,25 @@
+package screens
+
+import (
+	"mover/gamedata"
+
+	"github.com/hajimehoshi/ebiten/v2"
+)
+
+type ScreenManagerEvent int
+
+const (
+	EventNoop      ScreenManagerEvent = iota
+	EventReset                        // reset to initial scene
+	EventLoad                         // loading elements
+	EventReload                       // reload current scene
+	EventCompleted                    // current scene has completed
+	EventEndgame                      // shutdown all scenes
+)
+
+type Screen interface {
+	Update() error
+	Draw(screen *ebiten.Image)
+	SetEventHandler(e ScreenManagerEvent, f func())
+	SetDimensions(a gamedata.Area)
+}