added hidden doors/destroyable walls, fixed game reloading (tile clone)

components/destroyable.go

@@ -0,0 +1,29 @@
+package components
+
+import (
+	"log"
+
+	"github.com/hajimehoshi/ebiten/v2"
+)
+
+// A hidden door in a wall. If the player bumps into it once, it shows
+// damage and it vanishes the next time.
+
+type Destroyable struct {
+	Activated bool
+	Sprites   []*ebiten.Image
+	Current   int // sprite index
+}
+
+func (door *Destroyable) GetNext() *ebiten.Image {
+	if len(door.Sprites) > door.Current {
+		door.Current++
+		return door.Sprites[door.Current]
+	}
+
+	log.Fatalf("not enough sprites in transient tile, have %d sprites, index requested: %d",
+		len(door.Sprites), door.Current+1,
+	)
+
+	return nil
+}