diff --git a/lib/Ghost.cpp b/lib/Ghost.cpp
index 68f4eec..33acd00 100644
--- a/lib/Ghost.cpp
+++ b/lib/Ghost.cpp
@@ -178,7 +178,7 @@ void Ghost::updateDirection(const GameState & gameState) {
     if (opposite_direction)
       continue;
 
-    const GridPosition grid_position = { int64_t(move.position.x), int64_t(move.position.y) };
+    const GridPosition grid_position = { size_t(move.position.x), size_t(move.position.y) };
     const bool can_walk = isWalkableForGhost(grid_position, current_grid_position, isEyes());
     if (!can_walk)
       continue;
diff --git a/lib/Inky.cpp b/lib/Inky.cpp
index ab8d268..6b258ac 100644
--- a/lib/Inky.cpp
+++ b/lib/Inky.cpp
@@ -53,8 +53,8 @@ Position Inky::target(const GameState & gameState) const {
 
   // And selects a point on the line crossing blinky and this position that is at twice that distance
   // away from blinky
-  targetPosition.x += int64_t((targetPosition.x - blinkyPosition.x) / distanceBetweenBlinkyAndTarget) * 2;
-  targetPosition.y += int64_t((targetPosition.y - blinkyPosition.y) / distanceBetweenBlinkyAndTarget) * 2;
+  targetPosition.x += size_t((targetPosition.x - blinkyPosition.x) / distanceBetweenBlinkyAndTarget) * 2;
+  targetPosition.y += size_t((targetPosition.y - blinkyPosition.y) / distanceBetweenBlinkyAndTarget) * 2;
 
   return gridPositionToPosition(targetPosition);
 }
diff --git a/lib/PacMan.cpp b/lib/PacMan.cpp
index a78ea5f..c67f4ed 100644
--- a/lib/PacMan.cpp
+++ b/lib/PacMan.cpp
@@ -64,13 +64,13 @@ void PacMan::updateMazePosition(std::chrono::milliseconds time_delta) {
   auto moveToPosition = [position_delta](Position point, Direction move_direction) {
     switch (move_direction) {
       case Direction::LEFT:
-        return GridPosition{ int64_t(point.x - position_delta), int64_t(point.y) };
+        return GridPosition{ size_t(point.x - position_delta), size_t(point.y) };
       case Direction::RIGHT:
-        return GridPosition{ int64_t(point.x + pacman_size), int64_t(point.y) };
+        return GridPosition{ size_t(point.x + pacman_size), size_t(point.y) };
       case Direction::UP:
-        return GridPosition{ int64_t(point.x), int64_t(point.y - position_delta) };
+        return GridPosition{ size_t(point.x), size_t(point.y - position_delta) };
       case Direction::DOWN:
-        return GridPosition{ int64_t(point.x), int64_t(point.y + pacman_size) };
+        return GridPosition{ size_t(point.x), size_t(point.y + pacman_size) };
       case Direction::NONE:
       default:
         return positionToGridPosition(point);
diff --git a/lib/PacManAnimation.cpp b/lib/PacManAnimation.cpp
index 37e2b5e..7ad5716 100644
--- a/lib/PacManAnimation.cpp
+++ b/lib/PacManAnimation.cpp
@@ -32,7 +32,7 @@ void PacManAnimation::updateAnimationPosition(std::chrono::milliseconds time_del
     return;
 
   animation_position_delta += (0.02) * double(time_delta.count());
-  animation_position = int64_t(animation_position + animation_position_delta);
+  animation_position = size_t(animation_position + animation_position_delta);
 
   if (!dead)
       animation_position = animation_position % 4;
diff --git a/lib/include/Atlas.hpp b/lib/include/Atlas.hpp
index d5226f3..530d885 100644
--- a/lib/include/Atlas.hpp
+++ b/lib/include/Atlas.hpp
@@ -47,8 +47,8 @@ constexpr GridPosition eyeSprite(Direction direction) {
 
 constexpr GridPosition ghostSprite(Ghost ghost, Direction direction, bool alternative) {
   assert(ghost >= Ghost::blinky && ghost <= Ghost::clyde && "Invalid Ghost");
-  auto y = static_cast<int64_t>(ghost);
-  int64_t x = 0;
+  auto y = static_cast<size_t>(ghost);
+  size_t x = 0;
   switch (direction) {
     case Direction::RIGHT:
       x = 0;
diff --git a/lib/include/PacManAnimation.hpp b/lib/include/PacManAnimation.hpp
index 4c4e520..42dcde0 100644
--- a/lib/include/PacManAnimation.hpp
+++ b/lib/include/PacManAnimation.hpp
@@ -18,7 +18,7 @@ public:
   void pause();
 
 private:
-  int64_t animation_position = 0;
+  size_t animation_position = 0;
   double animation_position_delta = 0.0;
 };
 
diff --git a/lib/include/Position.hpp b/lib/include/Position.hpp
index 40eb798..712bff1 100644
--- a/lib/include/Position.hpp
+++ b/lib/include/Position.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <cmath>
+#include <cassert>
 
 namespace pacman {
 
@@ -10,13 +11,14 @@ struct Position {
 };
 
 struct GridPosition {
-  int64_t x;
-  int64_t y;
-  constexpr GridPosition(int64_t x, int64_t y) : x(x), y(y) {}
+  size_t x;
+  size_t y;
+  constexpr GridPosition(size_t x, size_t y) : x(x), y(y) {}
 };
 
 inline GridPosition positionToGridPosition(Position pos) {
-  return { int64_t(std::round(pos.x)), int64_t(std::round(pos.y)) };
+  assert(pos.x >= 0 && pos.y >= 0 && "Position should have positive values");
+  return { size_t(std::round(pos.x)), size_t(std::round(pos.y)) };
 }
 
 inline Position gridPositionToPosition(GridPosition pos) {