diff --git a/game/builtin/aoi2d_test.go b/game/builtin/aoi2d_test.go
index 5952ee9..30bed7a 100644
--- a/game/builtin/aoi2d_test.go
+++ b/game/builtin/aoi2d_test.go
@@ -1,7 +1,8 @@
-package builtin
+package builtin_test
 
 import (
 	"fmt"
+	"github.com/kercylan98/minotaur/game/builtin"
 	"github.com/kercylan98/minotaur/utils/random"
 	"testing"
 	"time"
@@ -29,7 +30,7 @@ func (slf *Ent) GetVision() float64 {
 }
 
 func TestNewAOI2D(t *testing.T) {
-	aoi := NewAOI2D(10000, 10000, 100, 100)
+	aoi := builtin.NewAOI2D(10000, 10000, 100, 100)
 
 	start := time.Now()
 	for i := 0; i < 50000; i++ {
diff --git a/game/builtin/ranking_list_example_test.go b/game/builtin/ranking_list_example_test.go
new file mode 100644
index 0000000..2dd4ece
--- /dev/null
+++ b/game/builtin/ranking_list_example_test.go
@@ -0,0 +1,77 @@
+package builtin_test
+
+import (
+	"fmt"
+	"github.com/kercylan98/minotaur/game/builtin"
+)
+
+func ExampleNewRankingList() {
+	ranklingList := builtin.NewRankingList[string, int](builtin.WithRankingListCount[string, int](10))
+
+	fmt.Println(ranklingList != nil)
+	// Output:
+	// true
+}
+
+func ExampleRankingList_Competitor() {
+	ranklingList := builtin.NewRankingList[string, int](builtin.WithRankingListCount[string, int](10))
+
+	scores := []int{6131, 132, 5133, 134, 135, 136, 137, 138, 139, 140, 222, 333, 444, 555, 666}
+	for i := 1; i <= 15; i++ {
+		ranklingList.Competitor(fmt.Sprintf("competitor_%2d", i), scores[i-1])
+	}
+
+	for rank, competitor := range ranklingList.GetAllCompetitor() {
+		fmt.Println(rank, competitor)
+	}
+
+	// Output:
+	// 0 competitor_ 1
+	// 1 competitor_ 3
+	// 2 competitor_15
+	// 3 competitor_14
+	// 4 competitor_13
+	// 5 competitor_12
+	// 6 competitor_11
+	// 7 competitor_10
+	// 8 competitor_ 9
+	// 9 competitor_ 8
+}
+
+func ExampleRankingList_RemoveCompetitor() {
+	ranklingList := builtin.NewRankingList[string, int](builtin.WithRankingListCount[string, int](10))
+
+	scores := []int{6131, 132, 5133, 134, 135, 136, 137, 138, 139, 140, 222, 333, 444, 555, 666}
+	for i := 1; i <= 15; i++ {
+		ranklingList.Competitor(fmt.Sprintf("competitor_%2d", i), scores[i-1])
+	}
+	ranklingList.RemoveCompetitor("competitor_ 1")
+	for rank, competitor := range ranklingList.GetAllCompetitor() {
+		fmt.Println(rank, competitor)
+	}
+
+	// Output:
+	// 0 competitor_ 3
+	// 1 competitor_15
+	// 2 competitor_14
+	// 3 competitor_13
+	// 4 competitor_12
+	// 5 competitor_11
+	// 6 competitor_10
+	// 7 competitor_ 9
+	// 8 competitor_ 8
+}
+
+func ExampleRankingList_GetRank() {
+	ranklingList := builtin.NewRankingList[string, int](builtin.WithRankingListCount[string, int](10))
+
+	scores := []int{6131, 132, 5133, 134, 135, 136, 137, 138, 139, 140, 222, 333, 444, 555, 666}
+	for i := 1; i <= 15; i++ {
+		ranklingList.Competitor(fmt.Sprintf("competitor_%2d", i), scores[i-1])
+	}
+
+	fmt.Println(ranklingList.GetRank("competitor_ 1"))
+
+	// Output:
+	// 0 <nil>
+}
diff --git a/game/builtin/ranking_list_test.go b/game/builtin/ranking_list_test.go
new file mode 100644
index 0000000..cf7e36a
--- /dev/null
+++ b/game/builtin/ranking_list_test.go
@@ -0,0 +1 @@
+package builtin_test