Simplified Mirri and Crawlspace by making their identical effects a common effect that is shared between them

Mage/src/main/java/mage/abilities/effects/common/continuous/ChangeMaxNumberThatCanAttackSourceEffect.java

@@ -0,0 +1,61 @@
+package mage.abilities.effects.common.continuous;
+
+import mage.abilities.Ability;
+import mage.abilities.effects.ContinuousEffectImpl;
+import mage.constants.Duration;
+import mage.constants.Layer;
+import mage.constants.Outcome;
+import mage.constants.SubLayer;
+import mage.game.Game;
+import mage.players.Player;
+
+/**
+ * @author LevelX2
+ */
+public class ChangeMaxNumberThatCanAttackSourceEffect extends ContinuousEffectImpl {
+
+    private final int maxAttackedBy;
+
+    public ChangeMaxNumberThatCanAttackSourceEffect(int maxAttackedBy) {
+        super(Duration.WhileOnBattlefield, Outcome.Benefit);
+        this.maxAttackedBy = maxAttackedBy;
+        staticText = "No more than " + (maxAttackedBy == 1 ? "one" : "two") + " creatures can attack you each combat";
+    }
+
+    public ChangeMaxNumberThatCanAttackSourceEffect(final ChangeMaxNumberThatCanAttackSourceEffect effect) {
+        super(effect);
+        this.maxAttackedBy = effect.maxAttackedBy;
+    }
+
+    @Override
+    public ChangeMaxNumberThatCanAttackSourceEffect copy() {
+        return new ChangeMaxNumberThatCanAttackSourceEffect(this);
+    }
+
+    @Override
+    public boolean apply(Layer layer, SubLayer sublayer, Ability source, Game game) {
+        if (layer != Layer.RulesEffects) {
+            return false;
+        }
+
+        Player controller = game.getPlayer(source.getControllerId());
+        if (controller == null) {
+            return false;
+        }
+        // Change the rule
+        if (controller.getMaxAttackedBy()> maxAttackedBy) {
+            controller.setMaxAttackedBy(maxAttackedBy);
+        }
+        return true;
+    }
+
+    @Override
+    public boolean apply(Game game, Ability source) {
+        return false;
+    }
+
+    @Override
+    public boolean hasLayer(Layer layer) {
+        return layer == Layer.RulesEffects;
+    }
+}