diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8605f97..4801ba0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -6,6 +6,14 @@ project(aocpp19
     LANGUAGES C CXX
 )
 
+include(CheckIPOSupported)
+check_ipo_supported(RESULT result OUTPUT output)
+if(result)
+  set(CMAKE_INTERPROCEDURAL_OPTIMIZATION TRUE)
+else()
+  message(WARNING "IPO is not supported: ${output}")
+endif()
+
 add_subdirectory(lib)
 
 add_executable(day02 day02.cpp)
diff --git a/day11.cpp b/day11.cpp
index fc0dae9..5d7315f 100644
--- a/day11.cpp
+++ b/day11.cpp
@@ -4,19 +4,17 @@
 #include <map>
 
 #include <intcode/intcode.hpp>
+#include <intcode/Grid.hpp>
 using namespace intcode;
 
 namespace {
 
-using Coord = std::pair<ValueType, ValueType>;
-
 auto Compute(Machine machine, ValueType start)
   -> std::map<Coord, ValueType> {
 
   Coord here {0,0};
   std::map<Coord, ValueType> paint {{here,start}};
-  ValueType dx {0};
-  ValueType dy {-1};
+  Coord dir {0, -1};
 
   bool next_color = true;
 
@@ -26,10 +24,8 @@ auto Compute(Machine machine, ValueType start)
       if (next_color) {
         paint[here] = o;
       } else {
-        std::swap(dx, dy);
-        (o ? dx : dy) *= -1;
-        here.first += dx;
-        here.second += dy;
+        dir = (o ? CW : CCW)(dir);
+        here = Add(here, dir);
       }
       next_color = !next_color;
     });
@@ -37,23 +33,6 @@ auto Compute(Machine machine, ValueType start)
   return paint;
 }
 
-auto Draw(std::ostream & out, std::map<Coord, ValueType> image) {
-  ValueType minX = 0, maxX = 0, minY = 0, maxY = 0;
-  for (auto&& [k, _] : image) {
-    auto [x,y] = k;
-    minX = std::min(minX, x);
-    maxX = std::max(maxX, x);
-    minY = std::min(minY, y);
-    maxY = std::max(maxY, y);
-  }
-  for (ValueType y = minY; y <= maxY; y++) {
-    for (ValueType x = minX; x <= maxX; x++) {
-      out << (image[{x,y}] ? "▓" : "░");
-    }
-    out << "\n";
-  }
-}
-
 } // namespace
 
 auto main() -> int {
diff --git a/day13.cpp b/day13.cpp
index 52db32d..02f150e 100644
--- a/day13.cpp
+++ b/day13.cpp
@@ -4,12 +4,11 @@
 #include <set>
 
 #include <intcode/intcode.hpp>
+#include <intcode/Grid.hpp>
 using namespace intcode;
 
 namespace {
 
-using Coord = std::pair<ValueType, ValueType>;
-
 auto Compute1(Machine machine)
   -> std::size_t {
   std::set<Coord> screen;
diff --git a/day15.cpp b/day15.cpp
index 1c2b344..9753cb9 100644
--- a/day15.cpp
+++ b/day15.cpp
@@ -1,85 +1,65 @@
-#include <iterator>
-#include <iostream>
-#include <utility>
-#include <tuple>
-#include <map>
 #include <deque>
-#include <vector>
+#include <iostream>
+#include <set>
+#include <tuple>
+#include <utility>
 
 #include <intcode/intcode.hpp>
+#include <intcode/Grid.hpp>
 using namespace intcode;
 
 namespace {
 
-using Coord = std::pair<ValueType, ValueType>;
+std::pair<ValueType, Coord(*)(Coord)> const moves[4]
+  {{1, Up}, {2, Down}, {3, Left}, {4, Right}};
 
-auto Compute(Machine machine) -> std::pair<int,int> {
-  Coord here {0,0};
-  std::map<Coord, ValueType> world {{{0,0},1}};
+auto Fork(Machine m, ValueType cmd) {
+  std::get<Input>(Step(m)).pos = cmd;
+  auto o = std::get<Output>(Step(m)).val;
+  return std::make_pair(o, std::move(m));
+}
 
-  using State = std::tuple<Coord, Machine>;
+auto Compute(Machine machine) {
+  Coord const origin {0,0};
+  std::set<Coord> world {origin};
 
-  std::vector<State> layer {{{0,0}, std::move(machine)}};
-  std::vector<State> next_layer;
+  std::deque<std::tuple<int, Coord, Machine>> todo
+    {{0, origin, std::move(machine)}};
 
-  auto action = [&](Machine m, ValueType cmd, Coord coord) {
-    if (!world.contains(coord)) {
-      std::get<Input>(Step(m)).pos = cmd;
-      auto o = std::get<Output>(Step(m)).val;
-      world[coord] = o;
-      if (o) {
-        next_layer.emplace_back(coord, std::move(m));
+  long part1 = -1;
+  long part2 = -1;
+
+top:
+  while (!todo.empty()) {
+    auto & [steps, loc, m] = todo.front();
+    part2 = steps;
+    steps++;
+
+    for (auto&& [cmd, fun] : moves) {
+      auto loc_ = fun(loc);
+      if (world.insert(loc_).second) {
+        auto [o,m_] = Fork(m, cmd);
+        switch (o) {
+          case 2:
+            part1 = steps;
+            world = {origin};
+            todo = {{0, origin, std::move(m_)}};
+            goto top;
+          case 1:
+            todo.emplace_back(steps, loc_, std::move(m_));
+        }
       }
     }
-  };
-
-  int part1 = 0;
-  while (!layer.empty()) {
-    for (auto && s : layer) {
-      auto& [loc, m] = s;
-      if (2 == world[loc]) {
-        world.clear();
-        world[loc] = 2;
-        auto start = std::move(m);
-        layer.clear();
-        layer.push_back({loc, std::move(start)});
-        goto loop2;
-      }
-      auto [x,y] = loc;
-      action(m, 1, {x,y-1});
-      action(m, 2, {x,y+1});
-      action(m, 3, {x-1,y});
-      action(std::move(m), 4, {x+1,y});
-    }
-    layer = std::move(next_layer);
-    next_layer.clear();
-    part1++;
+    todo.pop_front();
   }
 
-
-loop2:
-  int part2 = 0;
-  while (!layer.empty()) {
-    for (auto && s : layer) {
-      auto& [loc, m] = s;
-      auto [x,y] = loc;
-      action(m, 1, {x,y-1});
-      action(m, 2, {x,y+1});
-      action(m, 3, {x-1,y});
-      action(std::move(m), 4, {x+1,y});
-    }
-    layer = std::move(next_layer);
-    next_layer.clear();
-    part2++;
-  }
-  return {part1, part2-1};
+  return std::make_pair(part1,part2);
 }
 
 } // namespace
 
 auto main() -> int {
-  auto machine = Machine{ParseStream(std::cin)};
-  auto [part1, part2] = Compute(machine);
+  auto [part1, part2] = Compute(Machine{ParseStream(std::cin)});
   std::cout << "Part 1: " << part1 << std::endl;
   std::cout << "Part 2: " << part2 << std::endl;
 }
diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index e10e3fc..8a44164 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -1,2 +1,2 @@
-add_library(intcode src/Parser.cpp src/Interpreter.cpp src/Machine.cpp)
+add_library(intcode src/Grid.cpp src/Parser.cpp src/Interpreter.cpp src/Machine.cpp)
 target_include_directories(intcode PUBLIC include)
diff --git a/lib/include/intcode/intcode.hpp b/lib/include/intcode/intcode.hpp
index 7506259..fb11a8f 100644
--- a/lib/include/intcode/intcode.hpp
+++ b/lib/include/intcode/intcode.hpp
@@ -1,9 +1,9 @@
 #ifndef INTCODE_INTCODE_HPP_
 #define INTCODE_INTCODE_HPP_
 
+#include <intcode/Interpreter.hpp>
 #include <intcode/Machine.hpp>
 #include <intcode/Parser.hpp>
-#include <intcode/Interpreter.hpp>
 #include <Overload.hpp>
 
 #endif