user15234: It occurred to me that presumably every chess engine's score is based on the best available continuation move, and thus every other move must be worse (or at least no better).
i.e. if there were a move that the engine could immediately assess as being higher-scored than the computer's chosen move, then that would in fact be the engine's chosen move, and thus would be reflected in the engine's score of this position.
If all that is true, then I conclude that (in terms of position scores) Human Games consist of each side making moves which always either maintain or lower their score. i.e you only increase your score on your opponents turn, when they make sub-optimal moves.
i.e. from a computer's p.o.v. a human chess game is contest of two players making moves to see who can lose positional points the least.
Is this roughly accurate?
In particular, this:

you only increase your score on your opponents turn, when they make sub-optimal moves.


user15223: The answer is "no" and an example (+ detailed explanation) is given here. The brief explanation is that the depth the engine is looking at matters, and making one more move changes the depth the engine searches the main line.
You can find more examples looking at engine games. In this game, Stockfish evaluated the position after 8. Bxf6 as +1.76, then after the obvious recapture 8...Bxf6 its evaluation dropped to +1.40.

user18809: In that sense an engine's evaluation is not than different from an evaluation made by a human player who is much stronger than you.
If engines were "perfect", then yes, every move you make can only maintain or worsen the evaluation before the move (note also that in this world where engines are perfect the only possible evaluations are "White wins", "Draw" and "Black wins").
However, real-world engines aren't perfect. They can only analyze a position up to a certain depth. So it's totally possible that the engine evaluates a certain position as +0.5, then make a move and after the engine evaluates the new position, the score goes up.
The same can happen when you make the engine's best move though. In the same example of a position being valued as +0.5, if you follow the top engine moves until the end of the game, it won't stay as +0.5 forever (it's either gonna be a win or a draw, or, in case the engine got it totally wrong, perhaps even a loss).
Add to that the fact that engine evaluations are not set in stone even for a given position. The specific version engine you're using, the hardware it's running on, the time you've let the engine analyze and so on will have an impact on the number you get.

15234: <p>It occurred to me that presumably every chess engine's score is based on the best available continuation move, and thus every <em>other</em> move must be worse (or at least no better).</p>
<p>i.e. if there were a move that the engine could immediately assess as being higher-scored than the computer's chosen move, then that would in fact <em>be</em> the engine's chosen move, and thus would be reflected in the engine's score of this position.</p>
<p>If all that is true, then I conclude that (in terms of position scores) Human Games consist of each side making moves which always either maintain or lower their score. i.e you only increase your score on your opponents turn, when they make sub-optimal moves.</p>
<p>i.e. from a computer's p.o.v. a human chess game is contest of two players making moves to see who can lose positional points the least.</p>
<p>Is this roughly accurate?</p>
<p>In particular, this:</p>
<blockquote>
<p>you only increase your score on your opponents turn, when they make sub-optimal moves.</p>
</blockquote>
 15223: <p>The answer is &quot;no&quot; and an example (+ detailed explanation) is given <a href="https://chess.stackexchange.com/questions/29417/why-are-world-class-engines-playing-like-this/">here</a>. The brief explanation is that the depth the engine is looking at matters, and making one more move changes the depth the engine searches the main line.</p>
<p>You can find more examples looking at engine games. In <a href="https://tcec-chess.com/#div=sf&amp;game=94&amp;season=23" rel="nofollow noreferrer">this game</a>, Stockfish evaluated the position after 8. Bxf6 as +1.76, then after the obvious recapture 8...Bxf6 its evaluation dropped to +1.40.</p>
 18809: <p>In that sense an engine's evaluation is not than different from an evaluation made by a human player who is much stronger than you.</p>
<p>If engines were &quot;perfect&quot;, then yes, every move you make can only maintain or worsen the evaluation before the move (note also that in this world where engines are perfect the only possible evaluations are &quot;White wins&quot;, &quot;Draw&quot; and &quot;Black wins&quot;).</p>
<p>However, real-world engines aren't perfect. They can only analyze a position up to a certain depth. So it's totally possible that the engine evaluates a certain position as +0.5, then make a move and after the engine evaluates the new position, the score goes up.</p>
<p>The same can happen when you make the engine's best move though. In the same example of a position being valued as +0.5, if you follow the top engine moves until the end of the game, it won't stay as +0.5 forever (it's either gonna be a win or a draw, or, in case the engine got it totally wrong, perhaps even a loss).</p>
<p>Add to that the fact that engine evaluations are not set in stone even for a given position. The specific version engine you're using, the hardware it's running on, the time you've let the engine analyze and so on will have an impact on the number you get.</p>
