diff --git a/sjscript/src/sjscript/calculate.d b/sjscript/src/sjscript/calculate.d
index 39c2c2a..327187c 100644
--- a/sjscript/src/sjscript/calculate.d
+++ b/sjscript/src/sjscript/calculate.d
@@ -19,13 +19,18 @@ enum IsVarStore(T) =
 static assert(IsVarStore!(float[string]));
 
 ///
-struct NullVarStore {
+struct StandardVarStore {
  public:
   static float opIndex(string name) {
-    // TODO: error handling
-    throw new Exception("undefined variable %s".format(name));
+    switch (name) {
+      case "PI":   return PI;
+      case "PI_2": return PI_2;
+      case "PI_4": return PI_4;
+      case "E":    return E;
+      default: throw new Exception("undefined variable %s".format(name));
+    }
   }
-  static assert(IsVarStore!NullVarStore);
+  static assert(IsVarStore!StandardVarStore);
 }
 
 ///
diff --git a/sjscript/src/sjscript/parse.d b/sjscript/src/sjscript/parse.d
index eb2a033..5900e18 100644
--- a/sjscript/src/sjscript/parse.d
+++ b/sjscript/src/sjscript/parse.d
@@ -68,8 +68,8 @@ private class RuleSet {
       Expression end,
       @(TokenType.CloseBracket) Token) {
     return Period(
-        start.CalculateExpression(NullVarStore()),
-        end  .CalculateExpression(NullVarStore()));
+        start.CalculateExpression(StandardVarStore()),
+        end  .CalculateExpression(StandardVarStore()));
   }
 
   static Parameter[] ParseParameterListFirstItem(Parameter param) {
diff --git a/sjscript/test/test01.sj b/sjscript/test/test01.sj
index 1ec5d7f..1a0e36c 100644
--- a/sjscript/test/test01.sj
+++ b/sjscript/test/test01.sj
@@ -1,7 +1,5 @@
 // this is comment
 
-$define pi {3.14}
-
 $define sinwave {
   translate_x = $sinwave_add_x + sin(rtime * $sinwave_hz) * $sinwave_amp_x;
   translate_y = $sinwave_add_y + cos(rtime * $sinwave_hz) * $sinwave_amp_y;
@@ -18,7 +16,7 @@ $define shoot {
   translate_y += __dir_y;
 }
 
-$define beat {sin($pi/4)}
+$define beat {sin(PI/4)}
 A [$beat..$beat+10] {
   $define sinwave_add_x {0.5}
   $define sinwave_add_y {0.5}