Well you didn't just change what I suggested, but you changed more.
The player initialization can't be part of the window constructor (closing bracket before the player).
You can't call a function in the initialization list, but you have to use the constructor.
And the initialization list can't have a semicolon at the end.
Game::Game()
: window(sf::VideoMode(800, 600), "02_Game_Archi")
, player(150.f)
{
player.setFillColor(sf::Color::Blue);
player.Position(10.f, 20.f);
}
As you can see in my code, I also recommend to not use
using namespace sf; and instead just specifying it. Makes it a lot easier to read the code and see what is an SFML type and what isn't.
(Also I don' think you want a width of 8000
)