it is done

core/src/mindustry/game/Difficulty.java

@@ -0,0 +1,28 @@
+package mindustry.game;
+
+import arc.Core;
+
+/** Presets for time between waves. Currently unused.*/
+public enum Difficulty{
+    easy(1.4f),
+    normal(1f),
+    hard(0.5f),
+    insane(0.25f);
+
+    /** Multiplier of the time between waves. */
+    public final float waveTime;
+
+    private String value;
+
+    Difficulty(float waveTime){
+        this.waveTime = waveTime;
+    }
+
+    @Override
+    public String toString(){
+        if(value == null){
+            value = Core.bundle.get("setting.difficulty." + name());
+        }
+        return value;
+    }
+}