How do I interpret the analysis "Details"?

The "Details" section gives you the analysis of the computer. The essential information it gives you are the best variations it has found (a variation is a possible continuation of the game), the score of each variation, and the "depth" of the analysis it has been able to do for each variation.

The computer displays up to 4 of the best variations it has found for the side to move, one per line.

You can swipe the analysis to the left or right to see more than fits on the screen.

Let's say it's white to play, and we look at the details.

Here is what we could see on an iPad:

#1: d4 (+0.70 Depth 9)
    d4 d5 Bb5+

#2: d3 (+0.38 Depth 9)
    d3 Bg7 d4

#3: O-O (+0.36 Depth 9)
    O-O e5 Ng5

#4: Ng5 (+0.28 Depth 9)
    Ng5 d5 Bb5+

...and on an iPhone or iPod touch:

D9 +0.70 d4 d5 Bb5+
D9 +0.38 d3 Bg7 d4
D9 +0.36 O-O e5 Ng5
D9 +0.28 Ng5 d5 Bb5+

The first variation is always the best in the computer's opinion, but you should really keep in mind that all the variations shown are excellent. Inferior variations are simply not displayed at all, and so sometimes you will see less than 4 variations: if there are only 2 excellent moves for example, only these two will be shown. Please don't obsess over the order of the moves, because playing any of them will probably lead you to the victory anyway.

Every variation starts with what the computer considers as an excellent move for the side to move. You take the first move of every line (variation) and these are the moves the computer suggests to play in this position. For the example above, it means that the best moves are:

d4  (it means pawn to the d4 square)
d3  (pawn to the d3 square)
O-O  (short castle, a special move)
Ng5  (Knight to the g5 square)

After the variation's first move, you find the most probable continuation. For example in the first variation the computer thinks that after white has played pawn to d4, black will play d5 (pawn to d5) and white will then play Bb5+ (Bishop to b5, the plus sign reminding you that this move gives check).

For each variation, the score that is displayed represents how well the white side is doing if it plays this line. By default, all scores are from white's point of view, which is now standard in chess. You can change this in the Settings page.

A score near 0.00 means that white has no advantage over black.

A score around +1.00 means that white is approximately one pawn better than black. White may have a real advantage of exactly one pawn, or this advantage can come from a superior position with exactly the same material on both sides.

If the score is around -1.00, then white is behind by approximately one pawn or has positional weaknesses equivalent to being one pawn behind.

For higher or lower scores, the following standard scoring system is used:

Pawn = 1.00
Knight = 3.00
Bishop = 3.00
Rook = 5.00
Queen = 9.00

So a score of +2.00 could either mean that white has an advantage of 2 pawns, or 1 pawn and a much better position, or has traded a knight against a rook. Or any other combination...

Generally in grandmaster games an advantage of 2.00 or more is considered decisive. For amateur games, it must be more than that to say that the game is practically over.

A special case happens when the app has seen that one side could checkmate. In this case, the score will be represented as "+Mn" or "-Mn". For example, "+M2" means that white will mate in 2 moves, and "-M1" means that white will be checkmated on the next move.

The "Dx" or "Depth x" part represents the depth of the computation the app has done to find the best moves and the associated scores. It is the number of moves by each side (sometimes called the number of "half moves"). A depth of 2 means that the app has been able to compute every move by the side to move followed by every move of its opponent (that is, one move for each opponent).

A small depth like 4 or 5 is generally not enough to play well. Depths starting at 6 and above give good assessments of the position and of the best moves. A depth of 6 means that the computer has been able to compute all possible continuations on 3 full moves (3 moves by each side).

As you can guess, the higher the depth, the better the analysis.