SCOTCH GAME (for white)
This is the condensed (easy) version.

------------------
Main line 4... Bc5
------------------

Key variation:  1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Bc5 5.Be3 Qf6 6.c3 Nge7 7.Bc4 Ne5 8.Be2 Qg6
                9.O-O d6 10.f4 Qxe4 11.Bf2 Bxd4 12.cxd4 N5g6 13.Nc3 Qxf4 14.Nb5 O-O 15.Nxc7 Rb8 
                16.d5
     
1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Bc5 5.Be3 Qf6 6.c3 Nge7 7.Bc4 
       7... O-O 8.O-O 
       7... Qg6 8.O-O Qxe4 9.Nxc6 Qxc6 10.Bxf7+ Kxf7 11.Qh5+ 
       7... b6 8.Qd2 Qg6 9.f3 Bb7 10.b4 
      
1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Bc5 5.Be3 Qf6 6.c3 Nge7 7.Bc4 Ne5 8.Be2
       8... d5 9.O-O dxe4 10.Nb5 Bd6 (trap: if Bb6 11.Bxb6 Qxb6 12.Qd4) 11.Bc5
       8... Qg6 9.O-O
            9... O-O 10.Nd2 
            9... Qxe4 10.Nb5 Qc6 11.Bxc5 Qxc5 12.Qd4
            9... d6 10.f4 Qxe4 11.Bf2 Bxd4 12.cxd4 N5g6 13.Nc3 Qxf4 14.Nb5 O-O 15.Nxc7 Rb8 16.d5

-------------------------
Mieses variation 4... Nf6
-------------------------

Key variation:  1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Nf6 5.Nxc6 bxc6 6.e5 Qe7 7.Qe2 Nd5 8.c4 Ba6 
                9.b3 g6 10.g3 Bg7 11.Bb2 O-O 12.Bg2 Rae8 13.O-O Bxe5 14.Qxe5 Qxe5 15.Bxe5 Rxe5 
                16.cxd5 Bxf1 17.Kxf1 cxd5 18.Nc3 c6 19.Na4 Rfe8 20.Bf3

1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Nf6 5.Nxc6 bxc6 6.e5 
      6... Nd5 7.c4 Nb6 8.Bd3 Bb4+ 9.Bd2 
      6... Qe7 7.Qe2 Nd5 8.c4 Nb6 9.Nc3 
            9... a5 10.Bd2 a4 11.Qe4 
            9... Qe6 10.Qe4 Bb4 11.Bd2 
            9... g6 10.Ne4 Bg7 11.Bg5 Qb4+ 12.Qd2 Qxd2+ 13.Kxd2 Bxe5 14.Nf6+ Bxf6 15.Re1+

1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Nf6 5.Nxc6 bxc6 6.e5 Qe7 7.Qe2 Nd5 8.c4 Ba6 9.b3 g6 10.g3 Bg7 11.Bb2 
      11... 0–0–0 12.Bg2 Rhe8 13.0–0 Bxe5 14.Qxe5 Qxe5 15.Bxe5 Rxe5 16.cxd5 Bxf1 17.Kxf1 cxd5 
            18.Nc3 c6 19.Rc1 Kb8 20.Na4
      11... O-O 12.Bg2 Rae8 13.O-O Bxe5 14.Qxe5 Qxe5 15.Bxe5 Rxe5 16.cxd5 Bxf1 17.Kxf1 cxd5 
            18.Nc3 c6 19.Na4 Rfe8 20.Bf3

--- OR ---

1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Nf6 5.Nxc6 bxc6 6.e5 Qe7 7.Qe2 Nd5 8.c4 Ba6 9.b3 g6 10.f4 
      10... Bg7 11.Qf2 Nf6 12. Be2 Ne4 13. Qd4 Qb4+ 14. Nd2  Nxd2 15. Bxd2 Qe7 16. O-O
      10... Qb4+ 11.Bd2 Qb6 12.Nc3 Bb4 13.Qf3 Nxc3 14.Bxc3 Qd4 15.Rc1 Bxc3+ 16.Rxc3 0–0–0 17.Rd3 Qb6

---------------
Weird 4th moves
---------------

1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4
      4... Qh4 5.Nc3 Bb4 6.Be2 Qxe4 7.Ndb5 Bxc3+ 8.bxc3 Kd8 9.O-O 
            9... a6 10.Nd4 Nxd4 11.cxd4 Nf6 12.Bf3 Qg6 13.c4 
            9... Nf6 10.Bf3 Qc4 11.Rb1 Re8 12.Bg5