diff --git a/main.py b/main.py
index 26b1811..55a775d 100644
--- a/main.py
+++ b/main.py
@@ -2,7 +2,9 @@
 
 import matplotlib.pyplot as plt
 import pandas as pd
+from matplotlib.patches import FancyArrowPatch
 from matplotlib.widgets import Slider
+from mpl_toolkits.mplot3d import proj3d
 
 connection = [
     (0, 1),
@@ -25,6 +27,25 @@
 POINT_NAMES: List[str] = []
 
 
+# 3D arrow helper to draw arrows between 3D points
+class Arrow3D(FancyArrowPatch):
+    def __init__(self, xs, ys, zs, *args, **kwargs):
+        super().__init__((0, 0), (0, 0), *args, **kwargs)
+        self._verts3d = xs, ys, zs
+
+    def draw(self, renderer):
+        xs3d, ys3d, zs3d = self._verts3d
+        xs, ys, _ = proj3d.proj_transform(xs3d, ys3d, zs3d, self.axes.get_proj())
+        self.set_positions((xs[0], ys[0]), (xs[1], ys[1]))
+        super().draw(renderer)
+
+    def do_3d_projection(self, renderer=None):
+        xs3d, ys3d, zs3d = self._verts3d
+        xs, ys, zs = proj3d.proj_transform(xs3d, ys3d, zs3d, self.axes.get_proj())
+        self.set_positions((xs[0], ys[0]), (xs[1], ys[1]))
+        return max(zs)
+
+
 # Data class to hold thumb frame data
 class ThumbFrameData:
     def __init__(
@@ -113,6 +134,18 @@
         text = ax.text(p[0], p[1], p[2], name, fontsize=8)
         texts.append(text)
 
+    # Draw vector arrow from point 4 to 5 (thick red arrow)
+    arrow = Arrow3D(
+        [points[4][0], points[5][0]],
+        [points[4][1], points[5][1]],
+        [points[4][2], points[5][2]],
+        mutation_scale=20,
+        lw=4,
+        arrowstyle="-|>",
+        color="r",
+    )
+    ax.add_artist(arrow)
+
     ax.set_xlabel("X")
     ax.set_ylabel("Y")
     ax.set_zlabel("Z")
@@ -146,6 +179,13 @@
         for i, p in enumerate(points):
             texts[i].set_position((p[0], p[1], p[2]))
 
+        # Update arrow from point 4 to 5
+        arrow._verts3d = (
+            [points[4][0], points[5][0]],
+            [points[4][1], points[5][1]],
+            [points[4][2], points[5][2]],
+        )
+
         ax.set_title(f"Frame {data[frame_idx].frame_number}")
         fig.canvas.draw_idle()