diff --git a/compare/compare.go b/compare/compare.go
index a2a1837..e3cd33b 100644
--- a/compare/compare.go
+++ b/compare/compare.go
@@ -66,6 +66,7 @@ func GreaterOrEqual(left, right any) bool {
 }
 
 // InDelta checks if two values are equal or not within a delta.
+// Play: https://go.dev/play/p/TuDdcNtMkjo
 func InDelta[T constraints.Integer | constraints.Float](left, right T, delta float64) bool {
 	return float64(mathutil.Abs(left-right)) <= delta
 }
diff --git a/cryptor/basic.go b/cryptor/basic.go
index c0f5b7e..2b45f24 100644
--- a/cryptor/basic.go
+++ b/cryptor/basic.go
@@ -105,7 +105,7 @@ func HmacMd5(str, key string) string {
 }
 
 // HmacMd5WithBase64 return the hmac hash of string use md5 with base64.
-// todo
+// https://go.dev/play/p/UY0ng2AefFC
 func HmacMd5WithBase64(data, key string) string {
 	h := hmac.New(md5.New, []byte(key))
 	h.Write([]byte(data))