diff --git a/2019/inputs/15.txt b/2019/inputs/15.txt
new file mode 100644
index 0000000..7dbcaac
--- /dev/null
+++ b/2019/inputs/15.txt
@@ -0,0 +1 @@
+3,1033,1008,1033,1,1032,1005,1032,31,1008,1033,2,1032,1005,1032,58,1008,1033,3,1032,1005,1032,81,1008,1033,4,1032,1005,1032,104,99,101,0,1034,1039,1001,1036,0,1041,1001,1035,-1,1040,1008,1038,0,1043,102,-1,1043,1032,1,1037,1032,1042,1105,1,124,1002,1034,1,1039,1001,1036,0,1041,1001,1035,1,1040,1008,1038,0,1043,1,1037,1038,1042,1106,0,124,1001,1034,-1,1039,1008,1036,0,1041,101,0,1035,1040,1001,1038,0,1043,1002,1037,1,1042,1105,1,124,1001,1034,1,1039,1008,1036,0,1041,1002,1035,1,1040,101,0,1038,1043,1001,1037,0,1042,1006,1039,217,1006,1040,217,1008,1039,40,1032,1005,1032,217,1008,1040,40,1032,1005,1032,217,1008,1039,33,1032,1006,1032,165,1008,1040,33,1032,1006,1032,165,1101,2,0,1044,1106,0,224,2,1041,1043,1032,1006,1032,179,1101,0,1,1044,1106,0,224,1,1041,1043,1032,1006,1032,217,1,1042,1043,1032,1001,1032,-1,1032,1002,1032,39,1032,1,1032,1039,1032,101,-1,1032,1032,101,252,1032,211,1007,0,68,1044,1106,0,224,1101,0,0,1044,1105,1,224,1006,1044,247,1002,1039,1,1034,102,1,1040,1035,1001,1041,0,1036,1002,1043,1,1038,1001,1042,0,1037,4,1044,1105,1,0,67,55,37,80,63,12,30,78,95,7,20,63,83,54,86,58,97,11,84,24,11,77,42,78,22,54,89,52,44,28,93,30,81,60,58,78,87,60,54,59,78,96,17,82,74,85,66,41,89,96,54,40,82,17,22,89,65,96,71,55,81,34,90,11,85,44,58,83,79,93,30,76,62,80,16,73,20,43,40,73,69,39,39,15,93,39,99,8,74,33,97,84,24,50,91,5,71,34,81,76,22,98,50,93,80,36,76,16,76,43,19,71,63,41,21,99,40,75,55,27,82,80,83,54,66,75,61,86,14,10,74,38,92,31,49,97,20,98,15,71,59,96,53,86,35,60,6,73,71,59,79,10,84,69,23,82,14,7,76,99,45,19,96,92,14,63,55,71,46,71,34,74,73,22,95,89,10,24,59,69,17,42,96,12,92,94,66,1,69,91,36,90,94,13,17,33,46,20,89,90,24,12,94,92,83,42,73,43,70,83,55,17,92,66,23,74,99,1,92,82,54,71,96,1,22,78,74,94,66,78,40,87,13,87,73,74,89,26,26,70,42,79,3,9,84,72,55,98,56,27,73,74,57,85,66,76,88,55,58,30,97,40,71,76,6,10,55,71,43,36,99,46,59,34,37,84,61,85,90,62,98,18,39,46,84,23,70,93,9,71,5,71,94,5,59,40,71,26,90,12,45,57,74,5,92,86,32,99,20,92,82,22,44,88,29,41,89,7,86,81,72,76,9,94,94,3,8,94,71,12,93,6,82,91,91,20,86,86,38,85,95,42,86,85,19,57,90,17,85,6,84,17,81,42,77,63,26,59,9,24,85,22,31,35,93,64,90,4,16,91,67,83,23,43,63,75,3,88,93,52,14,84,85,36,95,12,51,79,54,1,16,72,1,76,79,88,63,95,77,6,91,86,23,92,54,91,51,82,45,14,98,89,74,47,52,82,80,65,74,44,58,90,14,98,42,91,6,50,88,29,81,96,25,1,97,62,62,73,61,48,82,76,93,98,49,14,74,6,97,30,47,73,77,8,89,10,17,65,21,74,95,43,83,89,72,96,27,59,20,58,80,10,70,86,42,92,26,50,98,85,3,62,20,93,86,78,19,78,91,23,90,37,71,66,97,97,95,86,40,46,79,70,37,14,98,51,91,81,4,9,77,93,19,53,70,87,40,11,95,25,93,90,17,98,39,76,92,55,57,93,39,76,13,99,58,92,26,88,80,65,34,71,62,72,17,64,38,97,85,32,4,88,69,82,51,63,61,71,77,33,90,59,74,49,76,8,76,93,55,36,71,84,7,67,47,3,85,98,9,99,32,8,79,18,28,55,77,10,30,79,77,4,1,99,82,66,90,41,64,22,82,33,20,87,24,29,80,53,72,27,17,85,84,70,16,94,11,81,92,48,85,61,47,83,21,45,92,92,38,61,75,98,52,73,80,29,82,94,29,85,61,69,59,35,84,86,60,98,63,83,69,39,10,15,64,18,85,88,63,97,95,56,13,43,75,93,13,34,85,57,37,96,39,65,60,73,73,82,11,81,80,38,88,76,23,88,19,70,2,93,46,28,79,92,91,18,6,92,96,50,77,56,45,77,36,64,83,91,64,75,48,72,71,17,69,40,82,7,6,92,70,25,23,72,9,23,84,16,17,75,76,70,60,61,99,86,21,27,85,63,80,81,55,87,93,97,53,78,53,97,14,97,49,85,65,91,72,72,5,93,34,81,10,85,86,81,19,87,61,84,11,99,96,94,8,78,13,84,9,70,0,0,21,21,1,10,1,0,0,0,0,0,0
diff --git a/2019/src/day15.cpp b/2019/src/day15.cpp
index 6fa383f..5a3ab27 100644
--- a/2019/src/day15.cpp
+++ b/2019/src/day15.cpp
@@ -1,10 +1,135 @@
 #include <iostream>
+#include <cassert>
+#include <unordered_set>
 #include "days.hpp"
+#include "utils.hpp"
+#include "point.hpp"
+
+namespace {
+    typedef aoc2019::Point<int, 2> point_t;
+
+    enum class Tile {
+        Wall,
+        Empty,
+        Oxygen,
+    };
+
+    enum class Mark {
+        None,
+        Temp,
+        Permanent,
+    };
+
+    const std::unordered_map<point_t, std::int64_t> DIRECTIONS{
+            {{0,  -1}, 1},
+            {{0,  1},  2},
+            {{-1, 0},  3},
+            {{1,  0},  4},
+    };
+
+    std::unordered_map<point_t, Tile> read_map(std::istream &input) {
+        aoc2019::IntCodeComputer computer(input);
+        std::deque<std::int64_t> output_buffer;
+        computer.connectOutput(output_buffer);
+
+        point_t pos = {0, 0};
+        std::deque<point_t> prev;
+        std::unordered_map<point_t, Tile> map{{pos, Tile::Empty}};
+        std::unordered_map<point_t, Mark> markings{{pos, Mark::Temp}};
+
+        computer.run();
+
+        while (true) {
+            std::optional<point_t> next_step;
+
+            for (auto &direction : DIRECTIONS) {
+                if (markings[pos + direction.first] == Mark::None) {
+                    next_step = direction.first;
+                    break;
+                }
+            }
+
+            if (next_step) {
+                const auto next_pos = pos + *next_step;
+                computer.sendInput(DIRECTIONS.at(*next_step));
+                computer.run();
+
+                assert(!output_buffer.empty());
+
+                switch (output_buffer.front()) {
+                    case 0:
+                        markings[next_pos] = Mark::Permanent;
+                        map[next_pos] = Tile::Wall;
+                        break;
+
+                    case 1:
+                    case 2:
+                        prev.push_front(pos);
+                        markings[next_pos] = Mark::Temp;
+                        map[next_pos] = static_cast<Tile>(output_buffer.front());
+                        pos = next_pos;
+                        break;
+
+                    default:
+                        throw std::domain_error("Invalid data from remote");
+                }
+                output_buffer.pop_front();
+                assert(output_buffer.empty());
+            } else {
+                markings[pos] = Mark::Permanent;
+                // Nowhere left to go, move back.
+                if (prev.empty()) {
+                    return map;
+                }
+
+                auto prev_pos = prev.front();
+                auto step = DIRECTIONS.at(prev_pos - pos);
+                prev.pop_front();
+                computer.sendInput(step);
+                computer.run();
+                // We should be able to travel back
+                assert(output_buffer.front() == 1);
+                output_buffer.pop_front();
+                pos = prev_pos;
+            }
+        }
+    }
+}
 
 void aoc2019::day15_part1(std::istream &input, std::ostream &output) {
-	output << "Not implemented\n";
+    const auto map = read_map(input);
+
+    std::deque<std::pair<point_t, int>> todo{{{0, 0}, 0}};
+    std::unordered_set<point_t> visited{{0, 0}};
+
+    while (!todo.empty()) {
+        auto [cur, dist] = todo.front();
+        todo.pop_front();
+
+        for (auto &dir : DIRECTIONS) {
+            auto new_pos = cur + dir.first;
+            if (!visited.count(new_pos)) {
+                visited.insert(new_pos);
+
+                switch (map.at(new_pos)) {
+                    case Tile::Empty:
+                        todo.emplace_back(new_pos, dist + 1);
+                        break;
+
+                    case Tile::Oxygen:
+                        output << dist + 1 << std::endl;
+                        return;
+
+                    default:
+                        break;
+                }
+            }
+        }
+    }
+
+    throw std::domain_error("No route to oxygen.");
 }
 
 void aoc2019::day15_part2(std::istream &input, std::ostream &output) {
-	output << "Not implemented\n";
+    output << "Not implemented\n";
 }
diff --git a/2019/src/utils.cpp b/2019/src/utils.cpp
index 3d3955f..1c8f1a8 100644
--- a/2019/src/utils.cpp
+++ b/2019/src/utils.cpp
@@ -135,12 +135,12 @@ void aoc2019::IntCodeComputer::run() {
                 }
                 break;
 
-            case 7: // equality
+            case 7: // less than
                 interpret_value(3) = interpret_value(1) < interpret_value(2);
                 ip += 4;
                 break;
 
-            case 8: // less than
+            case 8: // equality
                 interpret_value(3) = interpret_value(1) == interpret_value(2) ? 1 : 0;
                 ip += 4;
                 break;