diff --git a/Shared/Line.cs b/Shared/Line.cs
new file mode 100644
index 0000000..0a4c44c
--- /dev/null
+++ b/Shared/Line.cs
@@ -0,0 +1,46 @@
+using Microsoft.Xna.Framework;
+using System;
+using System.Collections.Generic;
+
+namespace SemiColinGames {
+  class Line {
+    public static Point[] Rasterize(Point p1, Point p2) {
+      return Line.Rasterize(p1.X, p1.Y, p2.X, p2.Y);
+    }
+
+    // Rasterizes a line using Bresenham's line-drawing algorithm.
+    //
+    // References:
+    // https://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm
+    // http://members.chello.at/~easyfilter/bresenham.html
+    // http://members.chello.at/~easyfilter/Bresenham.pdf (section 1.6)
+    public static Point[] Rasterize(int x1, int y1, int x2, int y2) {
+      int dx = Math.Abs(x2 - x1);
+      int stepX = x1 < x2 ? 1 : -1;
+      int dy = -Math.Abs(y2 - y1);
+      int stepY = y1 < y2 ? 1 : -1;
+      int error = dx + dy;
+      int errorXY = 0;   // Error value e_xy from the PDF.
+      // The size of the output is the size of the longer dimension, plus one.
+      int resultSize = Math.Max(dx, -dy) + 1;
+      var result = new Point[resultSize];
+
+      int i = 0;
+      result[0] = new Point(x1, y1);
+      while (x1 != x2 || y1 != y2) {
+        i++;
+        errorXY = 2 * error;
+        if (errorXY >= dy) {  // e_xy + e_x > 0
+          error += dy;
+          x1 += stepX;
+        }
+        if (errorXY <= dx) {  // e_xy + e_y < 0
+          error += dx;
+          y1 += stepY;
+        }
+        result[i] = new Point(x1, y1);
+      }
+      return result;
+    }
+  }
+}
diff --git a/Shared/Shared.projitems b/Shared/Shared.projitems
index 12c1794..009b974 100644
--- a/Shared/Shared.projitems
+++ b/Shared/Shared.projitems
@@ -15,6 +15,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)FpsCounter.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)History.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)IDisplay.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Line.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Player.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)SneakGame.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)World.cs" />
diff --git a/SharedTests/LineTests.cs b/SharedTests/LineTests.cs
new file mode 100644
index 0000000..5036aa7
--- /dev/null
+++ b/SharedTests/LineTests.cs
@@ -0,0 +1,269 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Microsoft.Xna.Framework;
+using System;
+using System.Collections.Generic;
+
+namespace SemiColinGames.Tests {
+  [TestClass]
+  public class LineTests {
+    [TestMethod]
+    public void TestRasterizeSinglePoint() {
+      var p1 = new Point(10, 10);
+      var expected = new Point[] { p1 };
+      var result = Line.Rasterize(p1, p1);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeHorizontal() {
+      var p1 = new Point(10, 10);
+      var p2 = new Point(15, 10);
+      var expected = new Point[] {
+        new Point(10, 10),
+        new Point(11, 10),
+        new Point(12, 10),
+        new Point(13, 10),
+        new Point(14, 10),
+        new Point(15, 10)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeHorizontalReverse() {
+      var p1 = new Point(15, 10);
+      var p2 = new Point(10, 10);
+      var expected = new Point[] {
+        new Point(15, 10),
+        new Point(14, 10),
+        new Point(13, 10),
+        new Point(12, 10),
+        new Point(11, 10),
+        new Point(10, 10)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeVertical() {
+      var p1 = new Point(10, 10);
+      var p2 = new Point(10, 15);
+      var expected = new Point[] {
+        new Point(10, 10),
+        new Point(10, 11),
+        new Point(10, 12),
+        new Point(10, 13),
+        new Point(10, 14),
+        new Point(10, 15)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeVerticalReverse() {
+      var p1 = new Point(10, 15);
+      var p2 = new Point(10, 10);
+      var expected = new Point[] {
+        new Point(10, 15),
+        new Point(10, 14),
+        new Point(10, 13),
+        new Point(10, 12),
+        new Point(10, 11),
+        new Point(10, 10)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeDiagonalPosPos() {
+      var p1 = new Point(0, 0);
+      var p2 = new Point(5, 5);
+      var expected = new Point[] {
+        new Point(0, 0),
+        new Point(1, 1),
+        new Point(2, 2),
+        new Point(3, 3),
+        new Point(4, 4),
+        new Point(5, 5)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeDiagonalPosNeg() {
+      var p1 = new Point(0, 5);
+      var p2 = new Point(5, 0);
+      var expected = new Point[] {
+        new Point(0, 5),
+        new Point(1, 4),
+        new Point(2, 3),
+        new Point(3, 2),
+        new Point(4, 1),
+        new Point(5, 0)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeDiagonalNegPos() {
+      var p1 = new Point(5, 0);
+      var p2 = new Point(0, 5);
+      var expected = new Point[] {
+        new Point(5, 0),
+        new Point(4, 1),
+        new Point(3, 2),
+        new Point(2, 3),
+        new Point(1, 4),
+        new Point(0, 5)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeDiagonalNegNeg() {
+      var p1 = new Point(5, 5);
+      var p2 = new Point(0, 0);
+      var expected = new Point[] {
+        new Point(5, 5),
+        new Point(4, 4),
+        new Point(3, 3),
+        new Point(2, 2),
+        new Point(1, 1),
+        new Point(0, 0)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeDoubleSlope() {
+      var p1 = new Point(0, 0);
+      var p2 = new Point(4, 9);
+      var expected = new Point[] {
+        new Point(0, 0),
+        new Point(0, 1),
+        new Point(1, 2),
+        new Point(1, 3),
+        new Point(2, 4),
+        new Point(2, 5),
+        new Point(3, 6),
+        new Point(3, 7),
+        new Point(4, 8),
+        new Point(4, 9)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeDoubleSlopePlusOne() {
+      var p1 = new Point(0, 0);
+      var p2 = new Point(5, 10);
+      var expected = new Point[] {
+        new Point(0, 0),
+        new Point(1, 1),
+        new Point(1, 2),
+        new Point(2, 3),
+        new Point(2, 4),
+        new Point(3, 5),
+        new Point(3, 6),
+        new Point(4, 7),
+        new Point(4, 8),
+        new Point(5, 9),
+        new Point(5, 10)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeDoubleSlopePlusOneReverse() {
+      var p1 = new Point(5, 10);
+      var p2 = new Point(0, 0);
+      var expected = new Point[] {
+        new Point(5, 10),
+        new Point(4, 9),
+        new Point(4, 8),
+        new Point(3, 7),
+        new Point(3, 6),
+        new Point(2, 5),
+        new Point(2, 4),
+        new Point(1, 3),
+        new Point(1, 2),
+        new Point(0, 1),
+        new Point(0, 0)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeHalfSlope() {
+      var p1 = new Point(0, 0);
+      var p2 = new Point(9, 4);
+      var expected = new Point[] {
+        new Point(0, 0),
+        new Point(1, 0),
+        new Point(2, 1),
+        new Point(3, 1),
+        new Point(4, 2),
+        new Point(5, 2),
+        new Point(6, 3),
+        new Point(7, 3),
+        new Point(8, 4),
+        new Point(9, 4)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeHalfSlopePlusOne() {
+      var p1 = new Point(0, 0);
+      var p2 = new Point(10, 5);
+      var expected = new Point[] {
+        new Point(0, 0),
+        new Point(1, 1),
+        new Point(2, 1),
+        new Point(3, 2),
+        new Point(4, 2),
+        new Point(5, 3),
+        new Point(6, 3),
+        new Point(7, 4),
+        new Point(8, 4),
+        new Point(9, 5),
+        new Point(10, 5)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+
+    [TestMethod]
+    public void TestRasterizeHalfSlopePlusOneReverse() {
+      var p1 = new Point(10, 5);
+      var p2 = new Point(0, 0);
+      var expected = new Point[] {
+        new Point(10, 5),
+        new Point(9, 4),
+        new Point(8, 4),
+        new Point(7, 3),
+        new Point(6, 3),
+        new Point(5, 2),
+        new Point(4, 2),
+        new Point(3, 1),
+        new Point(2, 1),
+        new Point(1, 0),
+        new Point(0, 0)
+      };
+      var result = Line.Rasterize(p1, p2);
+      CollectionAssert.AreEqual(expected, result);
+    }
+  }
+}
diff --git a/SharedTests/SharedTests.csproj b/SharedTests/SharedTests.csproj
index 741829e..c60ff41 100644
--- a/SharedTests/SharedTests.csproj
+++ b/SharedTests/SharedTests.csproj
@@ -8,7 +8,7 @@
     <ProjectGuid>{C86694A5-DD99-4421-AA2C-1230F11C10F8}</ProjectGuid>
     <OutputType>Library</OutputType>
     <AppDesignerFolder>Properties</AppDesignerFolder>
-    <RootNamespace>SharedTests</RootNamespace>
+    <RootNamespace>SemiColinGames.Tests</RootNamespace>
     <AssemblyName>SharedTests</AssemblyName>
     <TargetFrameworkVersion>v4.7.2</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
@@ -53,6 +53,7 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="HistoryTests.cs" />
+    <Compile Include="LineTests.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
   </ItemGroup>
   <ItemGroup>