Art: Made all trees 40% smaller + apple tree simple 2D flat style

src/systems/RiverSystem.js

@@ -6,7 +6,7 @@
  * - Biome-aware water coloring
  */
 
-export default class RiverSystem {
+class RiverSystem {
     constructor(worldWidth, worldHeight, biomeSystem) {
         this.worldWidth = worldWidth;
         this.worldHeight = worldHeight;