diff --git a/src/pegp/board.d b/src/pegp/board.d
new file mode 100644
index 0000000..c0a750d
--- /dev/null
+++ b/src/pegp/board.d
@@ -0,0 +1,60 @@
+module pegp.board;
+
+class Board
+{
+    private int m_size;
+    private bool[] m_pegs;
+
+    this(int size)
+    {
+        assert(size >= 3);
+        m_size = size;
+        const int n_pegs = (size * (size + 1)) / 2;
+        m_pegs = new bool[n_pegs];
+        m_pegs[] = true;
+        m_pegs[0] = false;
+    }
+
+    this(Board b)
+    {
+        m_size = b.m_size;
+        m_pegs = b.m_pegs.dup;
+    }
+
+    private int peg_index(int row, int col)
+    {
+        return (row * (row + 1)) / 2 + col;
+    }
+
+    bool valid_position(int row, int col)
+    {
+        return (row >= 0) && (row < m_size) && (col >= 0) && (col <= row);
+    }
+
+    bool peg_present(int row, int col)
+    {
+        return m_pegs[peg_index(row, col)];
+    }
+
+    unittest
+    {
+        Board b = new Board(5);
+        assert(b.valid_position(0, 0));
+        assert(b.valid_position(4, 0));
+        assert(b.valid_position(4, 4));
+        assert(b.valid_position(2, 2));
+        assert(b.valid_position(3, 1));
+        assert(!b.valid_position(0, 1));
+        assert(!b.valid_position(0, -1));
+        assert(!b.valid_position(5, 0));
+        assert(!b.valid_position(5, 4));
+        assert(!b.valid_position(4, 5));
+        assert(!b.valid_position(2, 3));
+        assert(!b.valid_position(0, 4));
+
+        assert(b.peg_present(1, 0));
+        assert(b.peg_present(1, 1));
+        assert(b.peg_present(4, 4));
+        assert(!b.peg_present(0, 0));
+    }
+}
diff --git a/src/pegp/main.d b/src/pegp/main.d
index 1ce868a..699507b 100644
--- a/src/pegp/main.d
+++ b/src/pegp/main.d
@@ -1,10 +1,10 @@
 module pegp.main;
 import std.stdio;
-import pegp.state;
+import pegp.board;
 
 int main(string[] args)
 {
-    State s = new State(3);
+    Board s = new Board(3);
     writeln("Peg Puzzle");
     return 0;
 }
diff --git a/src/pegp/state.d b/src/pegp/state.d
deleted file mode 100644
index 9c77dad..0000000
--- a/src/pegp/state.d
+++ /dev/null
@@ -1,60 +0,0 @@
-module pegp.state;
-
-class State
-{
-    private int m_size;
-    private bool[] m_pegs;
-
-    this(int size)
-    {
-        assert(size >= 3);
-        m_size = size;
-        const int n_pegs = (size * (size + 1)) / 2;
-        m_pegs = new bool[n_pegs];
-        m_pegs[] = true;
-        m_pegs[0] = false;
-    }
-
-    this(State s)
-    {
-        m_size = s.m_size;
-        m_pegs = s.m_pegs.dup;
-    }
-
-    private int peg_index(int row, int col)
-    {
-        return (row * (row + 1)) / 2 + col;
-    }
-
-    bool valid_position(int row, int col)
-    {
-        return (row >= 0) && (row < m_size) && (col >= 0) && (col <= row);
-    }
-
-    bool peg_present(int row, int col)
-    {
-        return m_pegs[peg_index(row, col)];
-    }
-
-    unittest
-    {
-        State s = new State(5);
-        assert(s.valid_position(0, 0));
-        assert(s.valid_position(4, 0));
-        assert(s.valid_position(4, 4));
-        assert(s.valid_position(2, 2));
-        assert(s.valid_position(3, 1));
-        assert(!s.valid_position(0, 1));
-        assert(!s.valid_position(0, -1));
-        assert(!s.valid_position(5, 0));
-        assert(!s.valid_position(5, 4));
-        assert(!s.valid_position(4, 5));
-        assert(!s.valid_position(2, 3));
-        assert(!s.valid_position(0, 4));
-
-        assert(s.peg_present(1, 0));
-        assert(s.peg_present(1, 1));
-        assert(s.peg_present(4, 4));
-        assert(!s.peg_present(0, 0));
-    }
-}