got 2 balls in 2 goal auto working
diff --git a/aos/common/commonmath.h b/aos/common/commonmath.h
index a77210f..f9337b2 100644
--- a/aos/common/commonmath.h
+++ b/aos/common/commonmath.h
@@ -4,7 +4,7 @@
 namespace aos {
 
 // Clips a value so that it is in [min, max]
-inline double Clip(double value, double min, double max) {
+static inline double Clip(double value, double min, double max) {
   if (value > max) {
     value = max;
   } else if (value < min) {
@@ -13,6 +13,15 @@
   return value;
 }
 
+template <typename T>
+static inline int sign(T val) {
+  if (val > T(0)) {
+    return 1;
+  } else {
+    return -1;
+  }
+}
+
 }  // namespace aos
 
 #endif  // AOS_COMMON_MATH_H_