add a guide for making scenes

This commit introduces a way to work with scenes by introducing a scene
type and a function to move between it.

examples/community/scene/README.md

@@ -0,0 +1,8 @@
+# Scene
+
+Created by [Jason Wangsadinata][jwangsadinata].
+
+This is just a simple example on how to create scenes in [Pixel][pixel].
+
+[jwangsadinata]: https://github.com/jwangsadinata
+[pixel]: https://github.com/faiface/pixel

examples/community/scene/main.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"github.com/faiface/pixel"
+	"github.com/faiface/pixel/pixelgl"
+	"golang.org/x/image/colornames"
+)
+
+type scene int
+
+const (
+	start scene = iota
+	menu
+	game
+	credits
+	end
+)
+
+func (s *scene) nextScene() {
+	*s = (*s + 1) % 5
+}
+
+func run() {
+	cfg := pixelgl.WindowConfig{
+		Title:  "Click On The Screen!",
+		Bounds: pixel.R(0, 0, 1024, 768),
+		VSync:  true,
+	}
+	win, err := pixelgl.NewWindow(cfg)
+	if err != nil {
+		panic(err)
+	}
+
+	s := start
+
+	for !win.Closed() {
+		switch s {
+		case start:
+			win.Clear(colornames.Lavender)
+		case menu:
+			win.Clear(colornames.Turquoise)
+		case game:
+			win.Clear(colornames.Lightyellow)
+		case credits:
+			win.Clear(colornames.Lightpink)
+		case end:
+			win.Clear(colornames.Sandybrown)
+		}
+
+		if win.JustPressed(pixelgl.MouseButtonLeft) {
+			s.nextScene()
+		}
+
+		win.Update()
+	}
+}
+
+func main() {
+	pixelgl.Run(run)
+}