diff --git a/sjscript/src/sjscript/ParametersBlock.d b/sjscript/src/sjscript/ParametersBlock.d
index bb91003..29d083b 100644
--- a/sjscript/src/sjscript/ParametersBlock.d
+++ b/sjscript/src/sjscript/ParametersBlock.d
@@ -34,6 +34,7 @@ struct Period {
 enum ParameterType {
   Assign,
   AddAssign,
+  OnceAssign,
 }
 
 ///
diff --git a/sjscript/src/sjscript/Token.d b/sjscript/src/sjscript/Token.d
index 529d3d9..8c54899 100644
--- a/sjscript/src/sjscript/Token.d
+++ b/sjscript/src/sjscript/Token.d
@@ -73,6 +73,7 @@ enum TokenType {
 
   @TextCompleteMatcher!"="  Assign,
   @TextCompleteMatcher!"+=" AddAssign,
+  @TextCompleteMatcher!":=" ColonAssign,
 
   @TextCompleteMatcher!"+" Add,
   @TextCompleteMatcher!"-" Sub,
diff --git a/sjscript/src/sjscript/parse.d b/sjscript/src/sjscript/parse.d
index c43fb93..df578d3 100644
--- a/sjscript/src/sjscript/parse.d
+++ b/sjscript/src/sjscript/parse.d
@@ -94,6 +94,14 @@ private class RuleSet {
     return Parameter(
         ident.text, ParameterType.AddAssign, expr, CreateTokenPos(ident, semicolon));
   }
+  static Parameter ParseOnceAssignParameter(
+      @(TokenType.Ident) Token ident,
+      @(TokenType.ColonAssign) Token,
+      Expression expr,
+      @(TokenType.SemiColon) Token semicolon) {
+    return Parameter(
+        ident.text, ParameterType.OnceAssign, expr, CreateTokenPos(ident, semicolon));
+  }
 
   static Expression ParseExpressionFromFirstTerm(Term term) {
     return Expression([term]);
diff --git a/sjscript/test/test01.sj b/sjscript/test/test01.sj
index 07c7661..931f608 100644
--- a/sjscript/test/test01.sj
+++ b/sjscript/test/test01.sj
@@ -1,16 +1,34 @@
 // this is comment
 
+$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;
+}
 $define horming {
   translate_x += cos(atan(player_y, player_x)) * $horming_speed;
   translate_y += sin(atan(player_y, player_x)) * $horming_speed;
 }
+$define shoot {
+  __dir_x := cos(atan(player_y, player_x)) * $shoot_speed;
+  __dir_y := sin(atan(player_y, player_x)) * $shoot_speed;
 
-A [0..10] {
-  translate_x = 0.5 + sin(rtime)*0.5;
-  translate_y = 0.5 + cos(rtime)*0.5;
+  translate_x += __dir_x;
+  translate_y += __dir_y;
 }
 
-B [5..15] {
+A [0..10] {
+  $define sinwave_add_x {0.5}
+  $define sinwave_add_y {0.5}
+  $define sinwave_amp_x {0.5}
+  $define sinwave_amp_y {0.5}
+  $define sinwave_hz    {2}
+  $sinwave
+}
+B [10..20] {
   $define horming_speed {0.1}
   $horming
 }
+C [20..30] {
+  $define shoot_speed {0.1}
+  $shoot
+}