diff --git a/core/theme/zelos.js b/core/theme/zelos.js
index 8ff63d3ba..de8461a2c 100644
--- a/core/theme/zelos.js
+++ b/core/theme/zelos.js
@@ -19,91 +19,71 @@ const Theme = goog.require('Blockly.Theme');
 let Zelos = {};
 
 Zelos.defaultBlockStyles = {
-  "colour_blocks": {
-    "colourPrimary": "#CF63CF",
-    "colourSecondary": "#C94FC9",
-    "colourTertiary": "#BD42BD"
+  'colour_blocks': {
+    'colourPrimary': '#CF63CF',
+    'colourSecondary': '#C94FC9',
+    'colourTertiary': '#BD42BD'
   },
-  "list_blocks": {
-    "colourPrimary": "#9966FF",
-    "colourSecondary": "#855CD6",
-    "colourTertiary": "#774DCB"
+  'list_blocks': {
+    'colourPrimary': '#9966FF',
+    'colourSecondary': '#855CD6',
+    'colourTertiary': '#774DCB'
   },
-  "logic_blocks": {
-    "colourPrimary": "#4C97FF",
-    "colourSecondary": "#4280D7",
-    "colourTertiary": "#3373CC"
+  'logic_blocks': {
+    'colourPrimary': '#4C97FF',
+    'colourSecondary': '#4280D7',
+    'colourTertiary': '#3373CC'
   },
-  "loop_blocks": {
-    "colourPrimary": "#0fBD8C",
-    "colourSecondary": "#0DA57A",
-    "colourTertiary": "#0B8E69"
+  'loop_blocks': {
+    'colourPrimary': '#0fBD8C',
+    'colourSecondary': '#0DA57A',
+    'colourTertiary': '#0B8E69'
   },
-  "math_blocks": {
-    "colourPrimary": "#59C059",
-    "colourSecondary": "#46B946",
-    "colourTertiary": "#389438"
+  'math_blocks': {
+    'colourPrimary': '#59C059',
+    'colourSecondary': '#46B946',
+    'colourTertiary': '#389438'
   },
-  "procedure_blocks": {
-    "colourPrimary": "#FF6680",
-    "colourSecondary": "#FF4D6A",
-    "colourTertiary": "#FF3355"
+  'procedure_blocks': {
+    'colourPrimary': '#FF6680',
+    'colourSecondary': '#FF4D6A',
+    'colourTertiary': '#FF3355'
   },
-  "text_blocks": {
-    "colourPrimary": "#FFBF00",
-    "colourSecondary": "#E6AC00",
-    "colourTertiary": "#CC9900"
+  'text_blocks': {
+    'colourPrimary': '#FFBF00',
+    'colourSecondary': '#E6AC00',
+    'colourTertiary': '#CC9900'
   },
-  "variable_blocks": {
-    "colourPrimary": "#FF8C1A",
-    "colourSecondary": "#FF8000",
-    "colourTertiary": "#DB6E00"
+  'variable_blocks': {
+    'colourPrimary': '#FF8C1A',
+    'colourSecondary': '#FF8000',
+    'colourTertiary': '#DB6E00'
   },
-  "variable_dynamic_blocks": {
-    "colourPrimary": "#FF8C1A",
-    "colourSecondary": "#FF8000",
-    "colourTertiary": "#DB6E00"
+  'variable_dynamic_blocks': {
+    'colourPrimary': '#FF8C1A',
+    'colourSecondary': '#FF8000',
+    'colourTertiary': '#DB6E00'
   },
-  "hat_blocks": {
-    "colourPrimary": "#4C97FF",
-    "colourSecondary": "#4280D7",
-    "colourTertiary": "#3373CC",
-    "hat": "cap"
+  'hat_blocks': {
+    'colourPrimary': '#4C97FF',
+    'colourSecondary': '#4280D7',
+    'colourTertiary': '#3373CC',
+    'hat': 'cap'
   }
 };
 
 Zelos.categoryStyles = {
-  "colour_category": {
-    "colour": "#CF63CF"
-  },
-  "list_category": {
-    "colour": "#9966FF"
-  },
-  "logic_category": {
-    "colour": "#4C97FF"
-  },
-  "loop_category": {
-    "colour": "#0fBD8C"
-  },
-  "math_category": {
-    "colour": "#59C059"
-  },
-  "procedure_category": {
-    "colour": "#FF6680"
-  },
-  "text_category": {
-    "colour": "#FFBF00"
-  },
-  "variable_category": {
-    "colour": "#FF8C1A"
-  },
-  "variable_dynamic_category": {
-    "colour": "#FF8C1A"
-  }
+  'colour_category': {'colour': '#CF63CF'},
+  'list_category': {'colour': '#9966FF'},
+  'logic_category': {'colour': '#4C97FF'},
+  'loop_category': {'colour': '#0fBD8C'},
+  'math_category': {'colour': '#59C059'},
+  'procedure_category': {'colour': '#FF6680'},
+  'text_category': {'colour': '#FFBF00'},
+  'variable_category': {'colour': '#FF8C1A'},
+  'variable_dynamic_category': {'colour': '#FF8C1A'}
 };
 
-Zelos =
-    new Theme('zelos', Zelos.defaultBlockStyles,
-        Zelos.categoryStyles);
+Zelos = new Theme('zelos', Zelos.defaultBlockStyles, Zelos.categoryStyles);
 
 exports = Zelos;