diff --git a/Shared/LinesOfSight.cs b/Shared/LinesOfSight.cs
new file mode 100644
index 0000000..29e9bf7
--- /dev/null
+++ b/Shared/LinesOfSight.cs
@@ -0,0 +1,80 @@
+using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Graphics;
+using System;
+
+namespace SemiColinGames {
+  class LinesOfSight {
+    public static void Draw(Player player, AABB[] collisionTargets, GraphicsDevice graphics,
+        BasicEffect lightingEffect) {
+      // TODO: DrawIndexedPrimitives
+      Color color = Color.FromNonPremultiplied(new Vector4(0, 0, 1, 0.6f));
+      Vector2 eyePos = player.EyePosition;
+      int numConePoints = 60;
+      // TODO: don't new[] every frame.
+      VertexPositionColor[] conePoints = new VertexPositionColor[numConePoints];
+      float visionRange = 150;
+      float visionRangeSq = visionRange * visionRange;
+      float fov = FMath.DegToRad(120);
+      float fovStep = fov / (numConePoints - 1);
+
+      Vector2 ray = new Vector2(visionRange * player.GetFacing, 0);
+      if (player.GetPose == Player.Pose.Stretching) {
+        ray = ray.Rotate(player.GetFacing * FMath.DegToRad(-30));
+      }
+      if (player.GetPose == Player.Pose.Crouching) {
+        ray = ray.Rotate(player.GetFacing * FMath.DegToRad(30));
+      }
+
+      for (int i = 0; i < conePoints.Length; i++) {
+        float angle = -fov / 2 + fovStep * i;
+        Vector2 rotated = ray.Rotate(angle);
+        Vector2 closestHit = Vector2.Add(eyePos, rotated);
+        float hitTime = 1f;
+
+        Vector2 halfTileSize = new Vector2(World.TileSize / 2.0f, World.TileSize / 2.0f);
+        for (int j = 0; j < collisionTargets.Length; j++) {
+          AABB box = collisionTargets[j];
+          if (Math.Abs(box.Position.X - player.Position.X) > visionRange + halfTileSize.X) {
+            continue;
+          }
+          Vector2 delta = Vector2.Add(halfTileSize, Vector2.Subtract(box.Position, eyePos));
+          if (delta.LengthSquared() > visionRangeSq) {
+            continue;
+          }
+          Hit? maybeHit = box.IntersectSegment(eyePos, rotated);
+          if (maybeHit != null) {
+            Hit hit = maybeHit.Value;
+            if (hit.Time < hitTime) {
+              hitTime = hit.Time;
+              closestHit = hit.Position;
+            }
+          }
+        }
+
+        float tint = 0.6f - hitTime / 2;
+        Color tinted = Color.FromNonPremultiplied(new Vector4(0, 0, 1, tint));
+        conePoints[i] = new VertexPositionColor(new Vector3(closestHit, 0), tinted);
+      }
+
+      // TODO: don't new[] every frame.
+      VertexPositionColor[] vertices = new VertexPositionColor[numConePoints * 3];
+      VertexPositionColor eyeVertex = new VertexPositionColor(new Vector3(eyePos, 0), color);
+      for (int i = 0; i < numConePoints - 1; i++) {
+        vertices[i * 3] = eyeVertex;
+        vertices[i * 3 + 1] = conePoints[i];
+        vertices[i * 3 + 2] = conePoints[i + 1];
+      }
+
+      VertexBuffer vertexBuffer = new VertexBuffer(
+          graphics, typeof(VertexPositionColor), vertices.Length, BufferUsage.WriteOnly);
+      vertexBuffer.SetData<VertexPositionColor>(vertices);
+
+      graphics.SetVertexBuffer(vertexBuffer);
+
+      foreach (EffectPass pass in lightingEffect.CurrentTechnique.Passes) {
+        pass.Apply();
+        graphics.DrawPrimitives(PrimitiveType.TriangleList, 0, vertices.Length / 3);
+      }
+    }
+  }
+}