diff --git a/sjplayer/src/sjplayer/Context.d b/sjplayer/src/sjplayer/Context.d
index e845600..016cd2c 100644
--- a/sjplayer/src/sjplayer/Context.d
+++ b/sjplayer/src/sjplayer/Context.d
@@ -38,7 +38,8 @@ class Context {
 
     import sjplayer.BackgroundScheduledController,
            sjplayer.CircleElement,
-           sjplayer.SquareElement;
+           sjplayer.SquareElement,
+           sjplayer.TriangleElement;
     auto factories = tuple(
         tuple(
           "actor",
@@ -61,6 +62,10 @@ class Context {
           "square",
           SquareElementScheduledControllerFactory(programs, varstore),
         ),
+        tuple(
+          "triangle",
+          TriangleElementScheduledControllerFactory(programs, varstore),
+        ),
         tuple(
           "variable",
           VarStoreScheduledControllerFactory(varstore),
diff --git a/sjplayer/src/sjplayer/ProgramSet.d b/sjplayer/src/sjplayer/ProgramSet.d
index 938c7b3..59ee795 100644
--- a/sjplayer/src/sjplayer/ProgramSet.d
+++ b/sjplayer/src/sjplayer/ProgramSet.d
@@ -8,7 +8,8 @@ import sjplayer.Actor,
        sjplayer.Background,
        sjplayer.CircleElement,
        sjplayer.PostEffect,
-       sjplayer.SquareElement;
+       sjplayer.SquareElement,
+       sjplayer.TriangleElement;
 
 ///
 class ProgramSet {
@@ -20,6 +21,7 @@ class ProgramSet {
       CircleElementProgram,
       PostEffectProgram,
       SquareElementProgram,
+      TriangleElementProgram,
     );
 
   ///
diff --git a/sjplayer/src/sjplayer/TriangleElement.d b/sjplayer/src/sjplayer/TriangleElement.d
new file mode 100644
index 0000000..2fa0016
--- /dev/null
+++ b/sjplayer/src/sjplayer/TriangleElement.d
@@ -0,0 +1,83 @@
+/// License: MIT
+module sjplayer.TriangleElement;
+
+import std.algorithm,
+       std.math,
+       std.typecons;
+
+import gl4d;
+
+import sjplayer.AbstractShapeElement,
+       sjplayer.ElementInterface,
+       sjplayer.ShapeElementDrawer,
+       sjplayer.ShapeElementProgram,
+       sjplayer.ShapeElementScheduledController,
+       sjplayer.util.linalg;
+
+///
+class TriangleElement : AbstractShapeElement {
+ public:
+  override DamageCalculationResult CalculateDamage(vec2 p1, vec2 p2) const {
+    if (!alive) return DamageCalculationResult(0, 0);
+
+    const m = matrix.inverse;
+    const a = (m * vec3(p1, 1)).xy;
+    const b = (m * vec3(p2, 1)).xy;
+
+    enum A = vec2( 0,  sqrt(3f)*2f/3f);
+    enum B = vec2(-1, -sqrt(3f)   /3f);
+    enum C = vec2( 1, -sqrt(3f)   /3f);
+
+    bool CheckInside(vec2 pt) {
+      return
+        cross2(B-A, pt-A) >= 0 && cross2(pt-A, C-A) >= 0 && cross2(C-B, pt-B) >= 0;
+    }
+    if (CheckInside(a) || CheckInside(b)) {
+      return DamageCalculationResult(damage, 0);
+    }
+
+    enum edges = [
+      tuple(A, B),
+      tuple(A, C),
+      tuple(B, C),
+    ];
+    float[3] distances;
+    static foreach (i, edge; edges) {
+      distances[i] = CalculateDistance2LineSegment(edge[0], edge[1], a, b);
+    }
+    const min_distance = distances[].minElement;
+
+    if (min_distance == 0) {
+      return DamageCalculationResult(damage, 0);
+    }
+    return DamageCalculationResult(0, 1-(min_distance-1).clamp(0f, 1f));
+  }
+}
+
+///
+alias TriangleElementDrawer = ShapeElementDrawer!(
+    TriangleElementProgram,
+    [vec2(-1, 1.2), vec2(-1, -1), vec2(1, -1), vec2(1, 1.2)]);
+
+///
+alias TriangleElementProgram = ShapeElementProgram!(q{
+    vec2 A = vec2( 0,  sqrt(3)*2/3);
+    vec2 B = vec2(-1, -sqrt(3)  /3);
+    vec2 C = vec2( 1, -sqrt(3)  /3);
+
+    vec2 AB = B - A;
+    vec2 AC = C - A;
+    vec2 BC = C - B;
+
+    float cross_AB = AB.x * (uv_.y - A.y) - AB.y * (uv_.x - A.x);
+    float cross_AC = (uv_.x - A.x) * AC.y - (uv_.y - A.y) * AC.x;
+    float cross_BC = BC.x * (uv_.y - B.y) - BC.y * (uv_.x - B.x);
+
+    return step(0, cross_AB) * step(0, cross_AC) * step(0, cross_BC);
+  });
+
+///
+alias TriangleElementScheduledControllerFactory =
+  ShapeElementScheduledControllerFactory!(
+      TriangleElement,
+      TriangleElementDrawer);
diff --git a/sjplayer/src/sjplayer/util/linalg.d b/sjplayer/src/sjplayer/util/linalg.d
index dad0398..2f7c929 100644
--- a/sjplayer/src/sjplayer/util/linalg.d
+++ b/sjplayer/src/sjplayer/util/linalg.d
@@ -33,10 +33,6 @@ unittest {
 
 ///
 float CalculateDistance2LineSegment(vec2 a1, vec2 b1, vec2 a2, vec2 b2) {
-  float cross2(vec2 v1, vec2 v2) {
-    return v1.x * v2.y - v1.y * v2.x;
-  }
-
   if (a1 == b1) return CalculateDistanceOriginAndLineSegment(a2 - a1, b2 - a1);
   if (a2 == b2) return CalculateDistanceOriginAndLineSegment(a1 - a2, b1 - a2);
 
@@ -77,3 +73,8 @@ unittest {
   assert(CalculateDistance2LineSegment(
         vec2(-1, 0), vec2(1, 0), vec2(2, 1), vec2(2, -1)).approxEqual(1f));
 }
+
+///
+float cross2(vec2 v1, vec2 v2) {
+  return v1.x * v2.y - v1.y * v2.x;
+}