diff --git a/demo_review_target.go b/demo_review_target.go
new file mode 100644
index 0000000..e1d6032
--- /dev/null
+++ b/demo_review_target.go
@@ -0,0 +1,38 @@
+package demo
+
+import (
+	"errors"
+	"strings"
+)
+
+func DoSomething(input string) (string, error) {
+	if input == "" {
+		return "", errors.New("empty")
+	}
+	result := input + "!"
+	return result, nil
+}
+
+func helper(x int) int {
+	if x < 0 {
+		x = 0
+	}
+	return x * 2
+}
+
+func ParseHost(rawURL string) string {
+	idx := strings.Index(rawURL, "://")
+	if idx == -1 {
+		return rawURL
+	}
+	rest := rawURL[idx+3:]
+	slash := strings.Index(rest, "/")
+	if slash == -1 {
+		return rest
+	}
+	return rest[:slash]
+}
+
+func DivideUnsafe(a, b int) int {
+	return a / b
+}