diff --git a/src/demo/bridge.cpp b/src/demo/bridge.cpp
index d6fde89..9c96986 100644
--- a/src/demo/bridge.cpp
+++ b/src/demo/bridge.cpp
@@ -11,9 +11,38 @@
 #include "assert.h"
 
 namespace demo {
+  void bridge::cable_interpolator::interp_add(float n)
+  {
+    const int points = particles_length / 2;
+
+    interp += n;
+    if (interp < 0) {
+      cable_ix -= 1;
+      assert(n < 0 && n >= -1);
+      interp = 1.0 + n;
+    }
+    if (interp > 1) {
+      cable_ix += 1;
+      assert(n > 0 && n <= 1);
+      interp = n;
+    }
+
+    if (cable_ix >= (points - 1)) {
+      interp = 1.0;
+      cable_ix = points - 2;
+    }
+
+    if (cable_ix < 0) {
+      interp = 0;
+      cable_ix = 0;
+    }
+  }
 
   mat4x4 bridge::init()
   {
+    interpolator.interp = 0.0;
+    interpolator.cable_ix = 0;
+
     // particles
     for (int i = 0; i < particles_length; i++) {
       float x = float(i / 2) * 2.0f - 5.0f;
@@ -52,11 +81,11 @@ namespace demo {
     for (int i = 0; i < rods_length; i++) {
       rods[i].particle[0] = &particles[i * 2];
       rods[i].particle[1] = &particles[i * 2 + 1];
-      rods[i].length = 3;
+      rods[i].length = 2;
     }
 
     mat4x4 view_trans
-      = translate(vec3(0.0, 0.0, 0.5))
+      = translate(vec3(0.0, 0.1, 0.5))
       * rotate_x(pi / 4)
       * rotate_y(pi / 12)
       * scale(vec3(-1, -1, 1));
@@ -73,11 +102,26 @@ namespace demo {
     printf("en cables %d\n", en_cables);
   }
 
+  void bridge::analog(float dx) {
+    interpolator.interp_add(dx * 0.5f);
+  }
+
   void bridge::_update()
   {
     for (int i = 0; i < particles_length; i++) {
       particles[i].force_accum = vec3(0, 0, 0);
-      particles[i].inverse_mass = 1.0f / 1.0f;
+
+      if ((i / 2) == interpolator.cable_ix) {
+        float mul = 1.0 - interpolator.interp;
+        assert(mul >= 0.0 && mul <= 1.0);
+        particles[i].inverse_mass = 1.0f / (1.0 + 10.0 * mul);
+      } else if ((i / 2) == (interpolator.cable_ix + 1)) {
+        float mul = interpolator.interp;
+        assert(mul >= 0.0 && mul <= 1.0);
+        particles[i].inverse_mass = 1.0f / (1.0 + 10.0 * mul);
+      } else {
+        particles[i].inverse_mass = 1.0f / 1.0f;
+      }
     }
 
     float duration = 1.f / 120.0f;
@@ -135,6 +179,31 @@ namespace demo {
     font::ter_u12n.draw_string(writer, center_p, "demo: bridge", 0xffffffff);
   }
 
+  static inline vec3 lerp(const vec3& a, const vec3& b, float f)
+  {
+    float dx = b.x - a.x;
+    float dy = b.y - a.y;
+    float dz = b.z - a.z;
+
+    return {
+      a.x + dx * f,
+      a.y + dy * f,
+      a.z + dz * f,
+    };
+  }
+
+  void bridge::draw_weight(ta_parameter_writer& writer, const mat4x4& trans)
+  {
+    vec3 p1 = particles[(interpolator.cable_ix * 2)].position;
+    vec3 p2 = particles[((interpolator.cable_ix + 1) * 2)].position;
+
+    vec3 p = lerp(p1, p2, interpolator.interp);
+    p.z = 0.0;
+
+    const vec3 color(1.0, 0.5, 0.0);
+    draw_cube(writer, trans * translate(p) * scale(0.3f), color);
+  }
+
   void bridge::draw(ta_parameter_writer& writer, const mat4x4& trans)
   {
     // punch through
@@ -144,7 +213,9 @@ namespace demo {
       ta_global_parameter::end_of_list(para_control::para_type::end_of_list);
 
     // opaque
-    draw_axis(writer, trans * scale(5.f));
+    draw_axis(writer, trans * scale(2.f));
+
+    draw_weight(writer, trans);
 
     // draw particles
     for (int i = 0; i < particles_length; i++) {
diff --git a/src/demo/bridge.hpp b/src/demo/bridge.hpp
index b13b764..ecd03a5 100644
--- a/src/demo/bridge.hpp
+++ b/src/demo/bridge.hpp
@@ -7,14 +7,25 @@
 namespace demo {
 
   struct bridge : scene {
+    struct cable_interpolator {
+      float interp;
+      int cable_ix;
+
+      void interp_add(float n);
+    };
+
+    cable_interpolator interpolator;
+
     mat4x4 init() override;
 
     void _update();
     void update() override;
 
     void draw_hud(ta_parameter_writer& writer);
+    void draw_weight(ta_parameter_writer& writer, const mat4x4& trans);
     void draw(ta_parameter_writer& writer, const mat4x4& trans) override;
     void a() override;
+    void analog(float dx) override;
 
     static const inline int particles_length = 12;
     physics::particle particles[particles_length];
diff --git a/src/demo/scene.hpp b/src/demo/scene.hpp
index 7df02b5..968745a 100644
--- a/src/demo/scene.hpp
+++ b/src/demo/scene.hpp
@@ -7,6 +7,7 @@ namespace demo {
 
   struct scene {
     virtual mat4x4 init() = 0;
+    virtual void analog(float dx) {}
     virtual void a() {}
     virtual void b() {}
     virtual void x() {}
diff --git a/src/platform/graphics.cpp b/src/platform/graphics.cpp
index e3406b6..f64737f 100644
--- a/src/platform/graphics.cpp
+++ b/src/platform/graphics.cpp
@@ -168,7 +168,7 @@ namespace graphics {
 
         auto& data = data_fields.data;
 
-        //float dx = static_cast<float>(data.analog_coordinate_axis[2] - 0x80) * 0.001;
+        float dx = static_cast<float>(data.analog_coordinate_axis[2] - 0x80) * 0.001;
         float dy = static_cast<float>(data.analog_coordinate_axis[3] - 0x80) * 0.001;
 
         bool a = ft0::data_transfer::digital_button::a(data.digital_button) == 0;
@@ -184,6 +184,8 @@ namespace graphics {
         last[port_ix].x = x;
         last[port_ix].y = y;
 
+        current_scene->analog(dx);
+
         view_trans = view_trans * rotate_y(dy);
       }
     }