So, Europe is between the longitudes 25°W to 65°E, so that means the exact center is 20°E. As a result whatever is left and right for 20°E (i.e. 10°E to 30°E) are the true Central European countries.
Well what'you know ... https://i.imgur.com/Cd3MZBF.jpeg
Phoenix Point, Space Marine 2 and World of Tanks