diff --git a/index.js b/index.js
index 27ddd6c..8f5d038 100644
--- a/index.js
+++ b/index.js
@@ -2,7 +2,7 @@
 
 /* global hexo */
 
-const mermaid = require('./mermaid.js');
+const mermaid = require('./lib/mermaid.js');
 
 hexo.config.mermaid = Object.assign({
   mmdcPath: 'mmdc',
@@ -11,9 +11,9 @@ hexo.config.mermaid = Object.assign({
   width: 800,
   height: 600,
   format: 'svg',
-  background: 'white',
+  background: 'transparent',
   scale: 1
 },
 hexo.config.mermaid);
 
-hexo.extend.tag.register('mermaid', mermaid(hexo.config.mermaid), { ends = true });
\ No newline at end of file
+hexo.extend.tag.register('mermaid', mermaid(hexo.config.mermaid), { ends: true });
\ No newline at end of file
diff --git a/lib/mermaid.js b/lib/mermaid.js
index 436a997..6e6eecd 100644
--- a/lib/mermaid.js
+++ b/lib/mermaid.js
@@ -6,28 +6,28 @@ function mermaid(config) {
   return function(args, content) {
     let options = Object.assign({}, config);
     let caption = '';
-    for (const arg in args) {
+    args.forEach(arg => {
       const arr = arg.split(':');
       if (arr.length == 1) {
         caption = arr;
       } else {
-        const { key, val } = arr;
+        const [ key, val ] = arr;
         options[key] = val;
       }
-    }
+    });
 
-    const args = [
-      '-t', options.theme || 'default',
-      '-w', options.width || 800,
-      '-H', options.height || 600,
-      '-e', options.format || 'svg',
-      '-b', options.background || 'white',
-      '-s', options.scale || 1,
+    const mmdcArgs = [
+      '-t', options.theme,
+      '-w', options.width,
+      '-H', options.height,
+      '-e', options.format,
+      '-b', options.background,
+      '-s', options.scale,
       '-i', '-',
       '-o', '-'
     ];
 
-    const result = spawnSync(options.mmdcPath, args, {
+    const result = spawnSync(options.mmdcPath, mmdcArgs, {
       cwd: process.cwd(),
       env: process.env,
       input: content,