refactor: header file for every module

include/islands.h

@@ -0,0 +1,31 @@
+#ifndef ISLANDS_H
+#define ISLANDS_H
+
+#include "engineSprite.h"
+#include <raylib.h>
+
+#define MAX_ISLANDS 14
+// Perimeter samples used to build each island's procedural shape (see
+// GenerateIsland in appGameIslands.c). Higher than you'd need for the old
+// small islands since they're now rendered at much higher native resolution
+// and a coarser sample count would show as flat facets on the coastline.
+#define ISLAND_SHAPE_POINTS 28
+
+typedef struct {
+  Vector2 position;
+  float radius; // collision radius (outer shore edge), in world units
+  Sprite sprite; // a small procedurally-painted texture, point-filtered like
+                 // the rest of the cast, not a shader effect
+} Island;
+
+typedef struct {
+  int count;
+  Island island[MAX_ISLANDS];
+} Islands;
+
+Islands CreateIslands(Camera2D *camera);
+void UpdateIslands(Islands *islands, Camera2D *camera);
+void RenderIslands(Islands *islands);
+void UnloadIslands(Islands *islands);
+
+#endif // ISLANDS_H