Answers.Body: <p>I think I can get 7 moves like this:</p>
  <pre><code>[FEN &quot;&quot;]
  1. h3 h5 2. Rh2 h4 3. a3 a5 4. Ra2 a4 5. f3 c6 6. Kf2 Qb6+ 7. e3 Qxe3+
  </code></pre>
  <ol>
  <li>h3 h5 (19)</li>
  <li>Rh2 h4 (18)</li>
  <li>a3 a5 (17)</li>
  <li>Ra2 a4 (16)</li>
  <li>f3 c6  (15)</li>
  <li>Kf2 Qb6+ (3)</li>
  <li>e3 Qxe3+ (1)</li>
  </ol>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-04-28T07:22:09.543Z
Answers.LastActivityDate: 2023-04-28T07:22:09.543Z
Answers.UserDisplayName: Steve Bennett
Answers.Body: <p>From the beginning position, in this case only a3 and h3 have a negative effect, and even with swapped colors, the opponent lacks one tempo to capture a rook. A check might be given, thought, thus a sequence might be -20- 1.a3 e6 -19- 2.h3 Qh4 -18- 3.d3 Bb4+ -6- 4.c3 Bxc3+ -4- 5.Nd2 Bxd2+ -3- 6.Qxd2 Qxf2+ -2- 7.Kd1. One move might be addable...Reeeeewan! :-)</p>
  
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Answers.CreationDate: 2023-04-28T07:07:54.213Z
Answers.LastActivityDate: 2023-04-28T07:07:54.213Z
Answers.UserDisplayName: Hauke Reddmann
Answers.Body: <p>I raise the bar to 8 moves, for Hauke.</p>
  <pre><code>[FEN &quot;&quot;]
  
  1. a3 a5 2. Ra2 a4 3. h3 h5 4. Rh2 h4 5. f3 e6 6. Rh1 Bc5 7. Rh2 Bd4 8. Rh1 Bf2+
  </code></pre>
  <ol>
  <li>a3 a5: 19</li>
  <li>Ra2 a4: 18</li>
  <li>h3 h5: 17</li>
  <li>Rh2 h4: 16</li>
  <li>f3 e6: 15</li>
  <li>Rh1 Bc5: 14</li>
  <li>Rh2 Bd4: 13</li>
  <li>Rh1 Bf2+: 1</li>
  </ol>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-04-28T10:05:27.067Z
Answers.LastActivityDate: 2023-04-28T10:05:27.067Z
Answers.UserDisplayName: Rewan Demontay
Answers.Body: <p>It seems to have been missed so far that f3 is also a possible reducing move it gains a king move, but loses both a knight and a pawn move. Therefore, we have a lot more choice and, in fact, a full 20 moves are possible:</p>
  <pre><code>[FEN &quot;&quot;]
  
  1. a3 a6 2. f3 a5 3. h3 b6 4. b4 a4 5. b5 e6 6. g3 Bb4 7. g4 g5 8. Bg2 Bc3 9. Bf1 Qf6 10. f4 Qxf4 11. Rh2 Qxh2 12. h4 Qxg1 13. h5 Ke7 14. h6 Kf6 15. e3 Bxd2+ 16. Kxd2 Qf2+ 17. Kd3 Qxe3+ 18. Kc4 d5+ 19. Kb4 c5+ 20. bxc6 Qc5#
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-04-28T18:23:06.823Z
Answers.Text: And now the same as shortest proof game :-) (Just joking, how shall one avoid swapping a3/f3/h3?)
Answers.UserDisplayName: Hauke Reddmann
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-04-29T22:15:44.633Z
Answers.Text: That's amazing. I did have F3 in my answer but didn't see b4.
Answers.UserDisplayName: Steve Bennett
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-05-01T00:51:52.587Z
Answers.Text: I particularly love move 6, where white gains axb and Bg2 but loses g3, d3 and d4.
Answers.UserDisplayName: Steve Bennett
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-04-28T13:51:35.560Z
Answers.LastActivityDate: 2023-04-28T23:40:03.147Z
Answers.LastEditDate: 2023-04-28T23:40:03.147Z
Answers.UserDisplayName: koedem
Body: <p>An easier version of <a href="https://chess.stackexchange.com/questions/42020/longest-sequence-of-moves-where-number-of-available-moves-increases?noredirect=1#comment69047_42020">this</a></p>
  <p>White has 20 available moves at the start of the game (from the standard position). After 1.h3 h5, white has 19 available moves. (The h pawn has lost the ability to move two squares, the knight can no longer move to h3, and the rook now has one new move, to h2.)</p>
  <p>What is the longest sequence of moves whereby white has at least 1 available move fewer than on the previous turn?</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2023-05-01T00:55:10.710Z
Comments.Text: I'm also curious to hear whether this problem has been posed before. Coming up with original problems is hard :)
Comments.UserDisplayName: Steve Bennett
Tags: <problems><records><mathematics>
Title: Longest sequence of moves where white's number of available moves decreases
ThreadText: # Longest sequence of moves where white's number of available moves decreases
  
  (Asked by: username_0 on 2023-04-28)
  
  An easier version of [this](https://chess.stackexchange.com/questions/42020/longest-sequence-of-moves-where-number-of-available-moves-increases?noredirect=1#comment69047_42020)
  
  White has 20 available moves at the start of the game (from the standard position). After 1.h3 h5, white has 19 available moves. (The h pawn has lost the ability to move two squares, the knight can no longer move to h3, and the rook now has one new move, to h2.)
  
  What is the longest sequence of moves whereby white has at least 1 available move fewer than on the previous turn?
  
  **Tags:** problems, records, mathematics
  
  > **Comments:**
  > **username_0**: I'm also curious to hear whether this problem has been posed before. Coming up with original problems is hard :)  
  
  ---
  
  ## 4 answers
  
  ### Answer by username_3 on 2023-04-28. Score: 8 | Accepted answer
  
  It seems to have been missed so far that f3 is also a possible reducing move it gains a king move, but loses both a knight and a pawn move. Therefore, we have a lot more choice and, in fact, a full 20 moves are possible:
  [FEN ""]
  
  1. a3 a6 2. f3 a5 3. h3 b6 4. b4 a4 5. b5 e6 6. g3 Bb4 7. g4 g5 8. Bg2 Bc3 9. Bf1 Qf6 10. f4 Qxf4 11. Rh2 Qxh2 12. h4 Qxg1 13. h5 Ke7 14. h6 Kf6 15. e3 Bxd2+ 16. Kxd2 Qf2+ 17. Kd3 Qxe3+ 18. Kc4 d5+ 19. Kb4 c5+ 20. bxc6 Qc5#
  
  > **Comments:**
  > **username_1**: And now the same as shortest proof game :-) (Just joking, how shall one avoid swapping a3/f3/h3?)  
  > **username_0**: That's amazing. I did have F3 in my answer but didn't see b4.  
  > **username_0**: I particularly love move 6, where white gains axb and Bg2 but loses g3, d3 and d4.  
  
  ---
  
  ### Answer by username_0 on 2023-04-28. Score: 3
  
  I think I can get 7 moves like this:
  [FEN ""]
  1. h3 h5 2. Rh2 h4 3. a3 a5 4. Ra2 a4 5. f3 c6 6. Kf2 Qb6+ 7. e3 Qxe3+
  
  
  h3 h5 (19)
  Rh2 h4 (18)
  a3 a5 (17)
  Ra2 a4 (16)
  f3 c6  (15)
  Kf2 Qb6+ (3)
  e3 Qxe3+ (1)
  
  
  ---
  
  ### Answer by username_1 on 2023-04-28. Score: 2
  
  From the beginning position, in this case only a3 and h3 have a negative effect, and even with swapped colors, the opponent lacks one tempo to capture a rook. A check might be given, thought, thus a sequence might be -20- 1.a3 e6 -19- 2.h3 Qh4 -18- 3.d3 Bb4+ -6- 4.c3 Bxc3+ -4- 5.Nd2 Bxd2+ -3- 6.Qxd2 Qxf2+ -2- 7.Kd1. One move might be addable...Reeeeewan! :-)
  
  
  ---
  
  ### Answer by username_2 on 2023-04-28. Score: 1
  
  I raise the bar to 8 moves, for Hauke.
  [FEN ""]
  
  1. a3 a5 2. Ra2 a4 3. h3 h5 4. Rh2 h4 5. f3 e6 6. Rh1 Bc5 7. Rh2 Bd4 8. Rh1 Bf2+
  
  
  a3 a5: 19
  Ra2 a4: 18
  h3 h5: 17
  Rh2 h4: 16
  f3 e6: 15
  Rh1 Bc5: 14
  Rh2 Bd4: 13
  Rh1 Bf2+: 1
  
  
  ---
  
  