Better commenting throughout

internal/hero/sprites.go

@@ -11,10 +11,12 @@ import (
 	"github.com/hajimehoshi/ebiten/v2"
 )
 
+// Asset paths
 const (
 	heroDir = "assets/hero"
 )
 
+// Animation state
 type animState int
 
 const (
@@ -27,6 +29,7 @@ type animationKey struct {
 	state     animState
 }
 
+// Sprite cache
 var (
 	knightAnimations map[animationKey][]*ebiten.Image
 )
@@ -47,6 +50,8 @@ func getKnightSprite(direction Direction, moving bool, frameIndex int) *ebiten.I
 	return frameFromSet(direction, state, frameIndex)
 }
 
+// Asset loading
+
 func loadKnightAnimations() error {
 	frames, err := loadAnimationFrames(heroDir)
 	if err != nil {
@@ -113,6 +118,8 @@ func loadImage(path string) (*ebiten.Image, error) {
 	return ebiten.NewImageFromImage(img), nil
 }
 
+// Image manipulation
+
 func flipImageHorizontally(img *ebiten.Image) *ebiten.Image {
 	bounds := img.Bounds()
 	w, h := bounds.Dx(), bounds.Dy()