feat: Prevent placing entities on water and improve land generation

render.js

@@ -31,6 +31,42 @@ function drawWorld() {
   animals.forEach((ani) => {
     if(!ani.dead) drawAnimal(ani);
   });
+  
+  // Draw placement indicator when in purchase mode
+  if (purchaseMode) {
+    drawPlacementIndicator();
+  }
+}
+
+// Draw a placement indicator at mouse position
+function drawPlacementIndicator() {
+  if (!lastMouseWorldX || !lastMouseWorldY) return;
+  
+  ctx.save();
+  ctx.translate(canvas.width/2 + offsetX, canvas.height/2 + offsetY);
+  ctx.scale(scale, scale);
+  
+  const isValid = isValidPlacement(lastMouseWorldX, lastMouseWorldY);
+  
+  // Draw indicator circle
+  ctx.beginPath();
+  ctx.arc(lastMouseWorldX, lastMouseWorldY, 15, 0, Math.PI*2);
+  ctx.strokeStyle = isValid ? "rgba(0, 255, 0, 0.7)" : "rgba(255, 0, 0, 0.7)";
+  ctx.lineWidth = 2/scale;
+  ctx.stroke();
+  
+  // Draw X if invalid
+  if (!isValid) {
+    ctx.beginPath();
+    ctx.moveTo(lastMouseWorldX - 10, lastMouseWorldY - 10);
+    ctx.lineTo(lastMouseWorldX + 10, lastMouseWorldY + 10);
+    ctx.moveTo(lastMouseWorldX + 10, lastMouseWorldY - 10);
+    ctx.lineTo(lastMouseWorldX - 10, lastMouseWorldY + 10);
+    ctx.strokeStyle = "rgba(255, 0, 0, 0.7)";
+    ctx.stroke();
+  }
+  
+  ctx.restore();
 }
 
 function drawTerrain() {