Implement hit object stacking algorithm.

src/itdelatrisu/opsu/Utils.java

@@ -250,6 +250,20 @@ public class Utils {
 		return val;
 	}
 
+	/**
+	 *
+	 * @param x1 The x-component of the first point
+	 * @param y1 The y-component of the first point
+	 * @param x2 The x-component of the second point
+	 * @param y2 The y-component of the second point
+	 * @return Euclidean distance between points (x1,y1) and (x2,y2)
+	 */
+	public static float distance(float x1, float y1, float x2, float y2) {
+		float v1 = Math.abs(x1 - x2);
+		float v2 = Math.abs(y1 - y2);
+		return (float) Math.sqrt((v1 * v1) + (v2 * v2));
+	}
+
 	/**
 	 * Returns true if a game input key is pressed (mouse/keyboard left/right).
 	 * @return true if pressed