diff --git a/packages/common/vpu-button.js b/packages/common/vpu-button.js
index 5e69a4fda9409870c0e97b4a94eed3e1f73ae692..39df25e1949c07055c73eb608e574ff1c1ff0a3f 100644
--- a/packages/common/vpu-button.js
+++ b/packages/common/vpu-button.js
@@ -8,6 +8,7 @@ class Button extends LitElement {
     constructor() {
         super();
         this.value = "";
+        // see: https://bulma.io/documentation/elements/button/#colors
         this.type = "primary";
         this.spinner = false;
         this.spinnerOnClick = true;