// ...

  bool canJump = false;
  bool canLeft = true;
  bool canRight = true;

  for (b2ContactEdge* ce = _playerBody->GetContactList(); ce; ce = ce->next) {
    b2Contact* c = ce->contact;

    if (c->IsTouching()) {
      b2WorldManifold worldManifold;
      c->GetWorldManifold(&worldManifold);

      // Math::dot...
      // Returns 0 when two vectors are perpendicular, > 0 when two vectors are in the same general direction,
      // 1 when two normalized vectors are parallel, < 0 when two vectors are in opposite general direction and
      // -1 when two normalized* vectors are antiparallel.

      if(Math::dot(Vector2(worldManifold.normal.x, worldManifold.normal.y), Vector2::yAxis(-1)) == 1) {
        canJump = true;
      }

      if(Math::dot(Vector2(worldManifold.normal.x, worldManifold.normal.y), Vector2::xAxis(-1)) == 1) {
        canLeft = false;
      }

      if(Math::dot(Vector2(worldManifold.normal.x, worldManifold.normal.y), Vector2::xAxis(1)) == 1) {
        canRight = false;
      }
    }
  }

  b2Vec2 vel = _playerBody->GetLinearVelocity();

  if (pressedKeys[KeyEvent::Key::Comma] && canJump) {
    vel.y = 8.f;
  }

  if (pressedKeys[KeyEvent::Key::A] && canLeft) {
    vel.x = -3.f;
  }

  if (pressedKeys[KeyEvent::Key::E] && canRight) {
    vel.x = 3.f;
  }

  _playerBody->SetLinearVelocity(vel);