diff --git a/lib/day9/day9.ex b/lib/day9/day9.ex
index 750a688..5a64935 100644
--- a/lib/day9/day9.ex
+++ b/lib/day9/day9.ex
@@ -65,13 +65,13 @@ defmodule Day9 do
   def repeat(_, 0), do: []
   def repeat(val, count), do: [val | repeat(val, count - 1)]
 
-  def run(state, parent, ip \\ 0)
+  def run(state, parent, ip \\ 0, debug \\ false)
 
-  def run(memory, parent, ip) when is_list(memory) do
-    run({memory, 0}, parent, ip)
+  def run(memory, parent, ip, debug) when is_list(memory) do
+    run({memory, 0}, parent, ip, debug)
   end
 
-  def run({memory, _relative_base} = state, parent, ip) when ip < length(memory) do
+  def run({memory, _relative_base} = state, parent, ip, debug) when ip < length(memory) do
     # IO.puts("IP: #{ip}")
     # IO.inspect(memory)
 
@@ -80,14 +80,34 @@ defmodule Day9 do
         send(parent, {:halt, self(), memory})
 
       {state, :cont, offset} ->
-        run(state, parent, ip + offset)
+        if debug do
+          receive do
+            :step ->
+              run(state, parent, ip + offset)
+
+            :abort ->
+              send(parent, {:abort, self(), state})
+          end
+        else
+          run(state, parent, ip + offset)
+        end
 
       {state, :jump, ip} ->
-        run(state, parent, ip)
+        if debug do
+          receive do
+            :step ->
+              run(state, parent, ip)
+
+            :abort ->
+              send(parent, {:abort, self(), state})
+          end
+        else
+          run(state, parent, ip)
+        end
     end
   end
 
-  def run(state, parent, _) do
+  def run(state, parent, _, _) do
     send(parent, {:ok, self(), state})
   end
 
@@ -101,9 +121,9 @@ defmodule Day9 do
     place = param + 2
 
     case op |> div(pow(10, place)) |> rem(10) do
-      0 -> Enum.at(memory, val)
-      1 -> val
-      2 -> Enum.at(memory, relative_base + val)
+      0 -> {Enum.at(memory, val), {:position, val}}
+      1 -> {val, {:immediate, val}}
+      2 -> {Enum.at(memory, relative_base + val), {:relative, val}}
     end
   end
 
@@ -111,8 +131,8 @@ defmodule Day9 do
     place = param + 2
 
     case op |> div(pow(10, place)) |> rem(10) do
-      2 -> relative_base + val
-      _ -> val
+      2 -> {relative_base + val, {:relative, val}}
+      _ -> {val, {:immediate, val}}
     end
   end
 
@@ -123,31 +143,38 @@ defmodule Day9 do
   end
 
   # halt
-  def eval([99 | _], memory, _) do
+  def eval([99 | _], memory, parent) do
+    send(parent, {:debug, "Halted", [], memory})
     {memory, :halt}
   end
 
   # add
-  def eval([op, a, b, dest | _], {memory, relative_base} = state, _) when opcode(op, 1) do
-    a_val = get_param(op, 0, a, state)
-    b_val = get_param(op, 1, b, state)
-    dest = get_write_param(op, 2, dest, state)
+  def eval([op, a, b, dest | _], {memory, relative_base} = state, parent) when opcode(op, 1) do
+    {a_val, a_param} = get_param(op, 0, a, state)
+    {b_val, b_param} = get_param(op, 1, b, state)
+    {dest, dest_param} = get_write_param(op, 2, dest, state)
+    new_state = {List.replace_at(memory, dest, a_val + b_val), relative_base}
+
+    send(parent, {:debug, "Add", [a_param, b_param, dest_param], new_state})
 
     {
-      {List.replace_at(memory, dest, a_val + b_val), relative_base},
+      new_state,
       :cont,
       4
     }
   end
 
   # multiply
-  def eval([op, a, b, dest | _], {memory, relative_base} = state, _) when opcode(op, 2) do
-    a_val = get_param(op, 0, a, state)
-    b_val = get_param(op, 1, b, state)
-    dest = get_write_param(op, 2, dest, state)
+  def eval([op, a, b, dest | _], {memory, relative_base} = state, parent) when opcode(op, 2) do
+    {a_val, a_param} = get_param(op, 0, a, state)
+    {b_val, b_param} = get_param(op, 1, b, state)
+    {dest, dest_param} = get_write_param(op, 2, dest, state)
+    new_state = {List.replace_at(memory, dest, a_val * b_val), relative_base}
+
+    send(parent, {:debug, "Multiply", [a_param, b_param, dest_param], new_state})
 
     {
-      {List.replace_at(memory, dest, a_val * b_val), relative_base},
+      new_state,
       :cont,
       4
     }
@@ -155,7 +182,7 @@ defmodule Day9 do
 
   # input
   def eval([op, addr | _], {memory, relative_base} = state, parent) when opcode(op, 3) do
-    addr = get_write_param(op, 0, addr, state)
+    {addr, addr_param} = get_write_param(op, 0, addr, state)
     send(parent, {:in, self()})
 
     res =
@@ -163,8 +190,12 @@ defmodule Day9 do
         {:in, val} -> val
       end
 
+    new_state = {List.replace_at(memory, addr, res), relative_base}
+
+    send(parent, {:debug, "Input", [addr_param], new_state})
+
     {
-      {List.replace_at(memory, addr, res), relative_base},
+      new_state,
       :cont,
       2
     }
@@ -172,68 +203,92 @@ defmodule Day9 do
 
   # output
   def eval([op, param | _], state, parent) when opcode(op, 4) do
-    out = get_param(op, 0, param, state)
+    {out, out_param} = get_param(op, 0, param, state)
     send(parent, {:out, self(), out})
 
+    send(parent, {:debug, "Output", [out_param], state})
     {state, :cont, 2}
   end
 
   # jump if non-zero
-  def eval([op, condition, ip | _], state, _) when opcode(op, 5) do
-    case get_param(op, 0, condition, state) do
-      0 ->
-        {state, :cont, 3}
+  def eval([op, condition, ip | _], state, parent) when opcode(op, 5) do
+    {cond_val, cond_param} = get_param(op, 0, condition, state)
+    {dest_val, dest_param} = get_param(op, 1, ip, state)
 
-      _ ->
-        {state, :jump, get_param(op, 1, ip, state)}
-    end
+    new_state =
+      case cond_val do
+        0 ->
+          {state, :cont, 3}
+
+        _ ->
+          {state, :jump, dest_val}
+      end
+
+    send(parent, {:debug, "Jump if non-zero", [cond_param, dest_param], new_state})
+    new_state
   end
 
   # jump if zero
-  def eval([op, condition, ip | _], state, _) when opcode(op, 6) do
-    case get_param(op, 0, condition, state) do
-      0 ->
-        {state, :jump, get_param(op, 1, ip, state)}
+  def eval([op, condition, ip | _], state, parent) when opcode(op, 6) do
+    {cond_val, cond_param} = get_param(op, 0, condition, state)
+    {dest_val, dest_param} = get_param(op, 1, ip, state)
 
-      _ ->
-        {state, :cont, 3}
-    end
+    new_state =
+      case cond_val do
+        0 ->
+          {state, :jump, dest_val}
+
+        _ ->
+          {state, :cont, 3}
+      end
+
+    send(parent, {:debug, "Jump if zero", [cond_param, dest_param], new_state})
+    new_state
   end
 
   # less than
-  def eval([op, a, b, dest | _], {memory, relative_base} = state, _) when opcode(op, 7) do
-    a_val = get_param(op, 0, a, state)
-    b_val = get_param(op, 1, b, state)
-    dest = get_write_param(op, 2, dest, state)
+  def eval([op, a, b, dest | _], {memory, relative_base} = state, parent) when opcode(op, 7) do
+    {a_val, a_param} = get_param(op, 0, a, state)
+    {b_val, b_param} = get_param(op, 1, b, state)
+    {dest, dest_param} = get_write_param(op, 2, dest, state)
 
-    memory =
+    new_state = {
       if a_val < b_val do
         List.replace_at(memory, dest, 1)
       else
         List.replace_at(memory, dest, 0)
-      end
+      end,
+      relative_base
+    }
 
-    {{memory, relative_base}, :cont, 4}
+    send(parent, {:debug, "Less than", [a_param, b_param, dest_param], new_state})
+    {new_state, :cont, 4}
   end
 
   # equals
-  def eval([op, a, b, dest | _], {memory, relative_base} = state, _) when opcode(op, 8) do
-    a_val = get_param(op, 0, a, state)
-    b_val = get_param(op, 1, b, state)
-    dest = get_write_param(op, 2, dest, state)
+  def eval([op, a, b, dest | _], {memory, relative_base} = state, parent) when opcode(op, 8) do
+    {a_val, a_param} = get_param(op, 0, a, state)
+    {b_val, b_param} = get_param(op, 1, b, state)
+    {dest, dest_param} = get_write_param(op, 2, dest, state)
 
-    memory =
+    new_state = {
       if a_val == b_val do
         List.replace_at(memory, dest, 1)
       else
         List.replace_at(memory, dest, 0)
-      end
+      end,
+      relative_base
+    }
 
-    {{memory, relative_base}, :cont, 4}
+    send(parent, {:debug, "Equal to", [a_param, b_param, dest_param], new_state})
+    {new_state, :cont, 4}
   end
 
   # set relative base
-  def eval([op, new_base | _], {memory, relative_base} = state, _) when opcode(op, 9) do
-    {{memory, relative_base + get_param(op, 0, new_base, state)}, :cont, 2}
+  def eval([op, new_base | _], {memory, relative_base} = state, parent) when opcode(op, 9) do
+    {new_base_val, new_base_param} = get_param(op, 0, new_base, state)
+    new_state = {memory, relative_base + new_base_val}
+    send(parent, {:debug, "Set relative base", [new_base_param], new_state})
+    {new_state, :cont, 2}
   end
 end
diff --git a/lib/intcode/assembler.ex b/lib/intcode/assembler.ex
index 506eed3..4305951 100644
--- a/lib/intcode/assembler.ex
+++ b/lib/intcode/assembler.ex
@@ -225,6 +225,22 @@ defmodule Assembler do
                  add #{a}, $#{dest}, #{dest}
                  """
 
+  assemble_macro ["div", a, b, dest],
+                 """
+                  mov 0, #{dest}
+                  mov #{a}, tmp
+                 do_sub:
+                   clt $tmp, #{b}, _self + 2
+                   jnz -1, end
+                   add 1, $#{dest}, #{dest}
+                   sub $tmp, #{b}, tmp
+                   jmp do_sub
+
+                 tmp: -1
+                 end:
+                 """
+                 |> IO.puts()
+
   assemble_macro ["not", src, dest],
                  """
                  sub 1, #{src}, #{dest}
diff --git a/lib/intcode/debugger.ex b/lib/intcode/debugger.ex
new file mode 100644
index 0000000..a53cf23
--- /dev/null
+++ b/lib/intcode/debugger.ex
@@ -0,0 +1,67 @@
+defmodule Debugger do
+  def run() do
+    program = [1, 1, 2, 3, 1102, 4, 5, 0, 99]
+    memory_view_length = floor(columns() / 7) * floor(rows() / 2 - 10)
+    memory = Day9.expand_memory(program, memory_view_length)
+
+    parent = self()
+
+    pid =
+      spawn(fn ->
+        Day9.run(memory, parent, 0, true)
+      end)
+
+    step(pid)
+  end
+
+  def columns do
+    {:ok, cols} = :io.columns()
+    cols
+  end
+
+  def rows do
+    {:ok, rows} = :io.rows()
+    rows
+  end
+
+  def step(pid) do
+    IO.write([IO.ANSI.clear(), IO.ANSI.home()])
+
+    receive do
+      {:debug, msg, params, {memory, _}} ->
+        print_memory(memory)
+        IO.puts("#{msg}: #{inspect(params)}")
+        IO.gets("")
+        send(pid, :step)
+        step(pid)
+
+      {msg, _, {memory, _}} when msg in [:halt, :abort, :ok] ->
+        print_memory(memory)
+        IO.gets("")
+    end
+  end
+
+  def print_memory(memory, row_size \\ nil)
+
+  def print_memory([], _) do
+  end
+
+  def print_memory(memory, row_size) when is_nil(row_size) do
+    print_memory(memory, floor(columns() / 7))
+  end
+
+  def print_memory(memory, row_size) do
+    memory
+    |> Enum.take(row_size)
+    |> Enum.each(fn val ->
+      val
+      |> to_string()
+      |> String.pad_leading(7)
+      |> IO.write()
+    end)
+
+    IO.write("\n\n")
+
+    print_memory(Enum.drop(memory, row_size), row_size)
+  end
+end
diff --git a/lib/intcode/vm.asm b/lib/intcode/vm.asm
new file mode 100644
index 0000000..d8ee611
--- /dev/null
+++ b/lib/intcode/vm.asm
@@ -0,0 +1,4 @@
+
+
+program:
+	data 1, 1, 2, 3