kutztown46: All evaluations by Fritz 9 at the ply indicated.
1. d4 Nf6 2. c4 e6 3. Nf3 b6 4. g3 Ba6 5. b3 Bb4+ 6. Bd2 Be7 7. Bg2 c6 8. Bc3 d5 9. Ne5 Nfd7 10. Nxd7 Nxd7 11. Nd2 f5 12. Rc1 O-O 13. O-O Rc8 14. Bb2 Bd6
15. a3 Qe7 (-.11/14)
16. Rc2 Nf6 (-.17/14) - Nf6 is 3rd choice of Fritz, after Bb7 (-.27), f4 (-.19)
17. Qc1 Kh8 (not in top six choices) - top 3 are Ne4 (-.29/14), Rcd8 (-.20), Qe8 (-.19).
18. e3 Ne4 (-.12/14) - Ne4 is 3rd choice of Fritz, after Bb7 (-.21), Kg8 (-.17).
19. Rd1 Bb7 (-.16/14)
20. b4 Bb8 (-.09/14) - Bb8 is 4th choice of Fritz, after Ba6 (-.28), Ng5 (-.17), Bc7 (-.15).
21. Bf1 Qe8 (-.25/14)
At this point, black seems fine, even though there are a number of possible improvements prior to this point (which I did not explore).
22. a4 a6 (not in top 6 choices) - top 5 are dxc4 (-.22/14), Qg6 (-.14), Qh5 (-.14), Kg8 (-.09), Rf6 (.00).
23. Nxe4 fxe4 (-.84/14)
The evaluation has shifted in black's favor. White had better choices at move 23: Bg2 (.01/14), a5 (-.02), Nf3 (-.07), f3 (-.07), Ba3 (-.08) or c5 (-.13).
24. b5 axb5 (-.84/14)
25. cxb5 Bd6 (-.71/14) - Bd6 was 2nd choice of Fritz, behind Rf6 (-.84).
26. Ba3 Bxa3 (-.15/16) - Bxa3 was 4th choice of Fritz, behind Qe7 (-.38), Qd7 (-.38), Qd8 (-.18).
27. Qxa3 Qf7 (.39/15).
Now the evaluation is positive for white. 27...Qf7 was Fritz's 6th choice. Top choice was cxb5 (.00).
28. Rdc1 c5 (1.14/20) - c5 was 6th choice of Fritz. Top choice was h6 (.59).
29. dxc5 Rxc5 (.81/16)
30. a5 Rxc2 (-.59/17)
The advantage has shifted back to black. 30. a5 was not in Fritz's top 6 choices. Top choice was Rxc5 (.76/15).
31. Rxc2 bxa5 (-.50/14)
32. b6 d4, which hands the advantage back to white. Fritz's top choice was Qf6 (-.82/16).
33. exd4 e5 - getting worse - e5 not in Fritz's top 6 choices. Top choice was Qf6 (.49/16).
34. Bc4 Qe8 (-2.78/14). Qe8 was Fritz's 3rd choice. Top choice was Qf3 (1.95).
35. d5 Qd8 (1.69/15)
Karpov could have strengthened his advantage with 35. dxe5 (2.75/15).
36. Qxa5 e3 - e3 not in Fritz's top 6 choices. Top choice was Qf6 (1.82/15).
37. fxe3 Qf6 (2.62/15).
Black is now down two pawns. I'll stop here.
Here is a possible improvement for black, starting at move 22, which leads to exciting play. Check it out! All moves top choice of Fritz 9, except where indicated.
22...dxc4 (-.22/14)
23. Nxc4 (-.15/14) c5 (-.18/14)
24. dxc5 (-.18/14) Ng5 (-.28/14)
25. Nd2 (.00/14) f4 (-.39/17)
26. Qa1 (-.07/14) fxe3 (-.20/14)
Now it really gets interesting...
27. Bxg7+ (-.20/14) Kg8
28. Bxf8 (.00/13) exf2+ (-.34/13)
29. Kxf2 Qxf8+ (-.25/12)
30. Kg1 (-.18/16)
A) 30...Qf5 (-.29/12)
31. c6 (-.12/15) Qxc2 (.00/14)
32. cxb7 (.00/13) Rd8 (.00/14)
33. Qf6 (.00/14) Nf7 (.00/12)
34. Be2 (.00/14) Rxd2 (.00/13)
35. Rf1 (.00/13) Qg6 (.00/12)
36. Qe7 (.00/13) Bxg3 (.00/13)
37. Qe8+ (.00/13) Kg7
38. hxg3 (.00/13) Qxg3+ (.00/13)
39. Kh1 Qh4+ (.00/13)
40. Kg1
and now what? - Fritz looks like it wants to achieve a draw by repetition with black.
-=\-=\-=\-=\-=\-=\-=\-=\-=\-=\-=\
B) 30...bxc5 (.00/15)
31. Bg2 (.00/14) Bxg2 (.00/14)
32. Kxg2 (.00/14) Qf5 (.00/15)
33. Rxc5 (.00/15) Rxc5 (.00/15)
34. bxc5 (.00/14) Qd5+ (.00/13)
35. Kf2 (.00/13) Nh3+ (.00/13)
36. Ke2 (.00/14) Be5 (.00/13)
37. Qb1 (.00/13) Qg2+ (.00/12)
38. Ke3 (.00/13) Qf2+ (.00/12)
and black's attack seems to peter out, with nothing better than a draw by repetition within five moves.