Compile looks_nextbackdrop and looks_nextcostume

src/compiler/compat-blocks.js

@@ -9,8 +9,6 @@ const stacked = [
     'control_get_counter',
     'control_incr_counter',
     'looks_changeeffectby',
-    'looks_nextbackdrop',
-    'looks_nextcostume',
     'looks_say',
     'looks_sayforsecs',
     'looks_seteffectto',

src/compiler/irgen.js

@@ -939,6 +939,14 @@ class ScriptTreeGenerator {
             return {
                 kind: 'looks.hide'
             };
+        case 'looks_nextbackdrop':
+            return {
+                kind: 'looks.nextBackdrop'
+            };
+        case 'looks_nextcostume':
+            return {
+                kind: 'looks.nextCostume'
+            };
         case 'looks_setsizeto':
             return {
                 kind: 'looks.setSize',

src/compiler/jsgen.js

@@ -725,6 +725,12 @@ class JSGenerator {
             this.source += 'target.setVisible(false);\n';
             this.source += 'runtime.ext_scratch3_looks._renderBubble(target);\n';
             break;
+        case 'looks.nextBackdrop':
+            this.source += 'stage.setCostume(stage.currentCostume + 1);\n';
+            break;
+        case 'looks.nextCostume':
+            this.source += 'target.setCostume(target.currentCostume + 1);\n';
+            break;
         case 'looks.setSize':
             this.source += `target.setSize(${this.descendInput(node.size).asNumber()});\n`;
             break;