Add examples catalog with subcommand dispatch

- Extract game engine from package main to engine/ library package
- Create examples/ package with registry, Entry type, and BuilderDeps
- Register default world as an example (moved from main())
- Add combat example: two teams of units facing each other
- Rewrite main.go as thin dispatch: go run . example [name]
- Update README with examples catalog one-liner

1 files changed, 33 insertions, 0 deletions

diff --git a/engine/image.go b/engine/image.go
new file mode 100644
index 0000000..07cac55
--- /dev/null
+++ b/engine/image.go
@@ -0,0 +1,33 @@
+package engine
+
+import (
+	"age_of_empires/physics"
+	"image/color"
+
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/vector"
+)
+
+func NewFilledRectangleImage(size physics.Point, color color.Color) *ebiten.Image {
+	image := ebiten.NewImage(size.X, size.Y)
+	image.Fill(color)
+	return image
+}
+
+func NewStrokeRectangleImage(size physics.Point, strokeWidth float32, color color.Color) *ebiten.Image {
+	image := ebiten.NewImage(size.X, size.Y)
+	vector.StrokeRect(image, 0, 0, float32(size.X), float32(size.Y), float32(strokeWidth), color, true)
+	return image
+}
+
+func NewFilledCircleImage(width int, color color.Color) *ebiten.Image {
+	image := ebiten.NewImage((width), (width))
+	vector.DrawFilledCircle(image, float32(width/2), float32(width/2), float32(width/2), color, true)
+	return image
+}
+
+func NewStrokeCircleImage(width int, strokeWidth int, color color.Color) *ebiten.Image {
+	image := ebiten.NewImage((width), (width))
+	vector.StrokeCircle(image, float32(width/2), float32(width/2), float32(width/2), float32(strokeWidth), color, true)
+	return image
+}