This month we will examine how you can play against Rybka (or another chess engine) in Aquarium. The Play mode in Aquarium has been revised and streamlined in the upcoming Aquarium 3.2 version. As usual many of the improvements are based on user feedback.

Handicap Play

Besides the option to play against a chess engine at full strength with a rating in the vicinity of 3000 Elo, Aquarium offers a variety of engine handicap methods:

1. Skill handicap. You can choose from three different methods for reducing the strength of the engine.
2. Material handicap ranging from those suitable for the beginner to the grandmaster.
3. Time handicap. Assign a faster time control to the engine than yourself.
4. Depth handicap. Weaken the engine by limiting its search depth.

You can combine these handicap methods any way you like, except of course items three and four, which are mutually exclusive.

Skill handicap allows you to choose a wide rating range for the engine, from the novice level (700) up to IM or GM level (2500). For the lower rating levels a special handicap engine is used, which the developers found to make more human-like mistakes than the other engines.

If you want to play against the engine at full strength, but still have reasonable winning chances, then material handicaps are an interesting option. Here you start the game with a material advantage that may allow you to draw or win even if you blunder.

Time handicap and depth handicap decrease the strength of the engine and speed up the game at the same time. By giving the engine a very short time or restricting it to a low search depth you can finish a game in half the time (compared to equal time for both sides) as the engine will respond immediately to your moves.

It’s worth mentioning in this connection that you can also play blindfold games and semi-blindfold games (where all pieces look the same) against the engine. In that case you could also use one or more of the four handicap methods mentioned above to weaken the engine’s play.

Note that you have the option to play your games either in tournament mode or fun mode. In tournament mode the rules are basically the same as in normal tournament games where no take-backs or assistance is allowed. Players doing serious preparation for a tournament can choose this mode. In fun mode you are allowed to take back moves, get hints from Aquarium, etc. so this is the right mode if you want to relax by playing a casual game of chess.

	Play Mode There is a special play mode in Aquarium where you can play against Rybka and other chess engines. You switch to play mode by clicking the big Play button in the sidebar. The idea behind play mode is to give you everything you need to play a game of chess without unrelated features getting in your way. This is what play mode usually looks like. Here you see the sidebar (Navigation Pane) running down the left side and the Ribbon at the top. The working area shows the board on the left and on the right-hand side we have the clocks at the top, then the game itself and finally the opening book. The opening book window can be closed if you like.
		Play mode with the ribbon and the sidebar.

	If you want even more space for the board, simply click F11 and both the ribbon at the top and the sidebar will be minimized. Press F11 again when you want to restore the window to its previous state.
Play mode with maximized working area.

	User Profiles You may remember from my column about Peshk@ that the program keeps track of the performance of different users. You simply need to define a user profile for each of them. Aquarium uses a similar system. After switching to play mode, click the player name in the sidebar. Aquarium comes with a default user profile called “Player,” so that will be the name you see before you add your own user profile. In the illustration below, I’m about to add a third user profile. I opened the “Select player profile” dialog box by clicking the player name; Lisa in this example (highlighted in the illustration), and then I clicked the “New…” button and the “New profile” dialog was displayed. Here I must type the name of the player in the “Name” field and the estimated rating in the “Rating” field. When I click OK, the new player profile will be created.
		User profiles.

The illustration shows that I have already created two user profiles: John, with an estimated rating of 1200 and Lisa with a 1600 rating. The “Games” column shows that neither of them has played a game yet. If John wanted to play a game against Rybka, he would select his name from the list and click OK.

Besides creating user profiles for different persons, you may also want to create two or more profiles for yourself. You could, for instance, use one profile for serious training games and a different one for casual games.

As I have done before, I will warn you that the ratings in Aquarium may vary considerably from the rating level to which you are accustomed. The underlying problem is that there is no fixed mapping between chess strength and rating level, so different rating pools (e.g. different countries) use different rating levels. When it comes to playing chess engines, other factors such as the speed of your computer, the effect of different handicap methods, etc. can affect chess engines in various ways.

Starting a New Game You can start playing a game from the Aquarium menu, the Quick Access Toolbar, directly in play mode or you can start from any position in a game you are viewing from a database or in the Sandbox. The first method is to click the Aquarium button in the upper left corner of the window, select Play and then New Game as shown below. Here you can also start a new FischerRandom or Chess960 game, start a new game from a position that you define or you can change the play options.

Start play from the Aquarium menu.

The second method is to start a game from the Quick Access Toolbar (QAT).

	Click the clock icon (highlighted in the image above) to start a new game. The advantage of the QAT icon is that it is always visible. The clock icon is not displayed by default, so you need to add it by right-clicking over the QAT and selecting “Customize”.
		Start play from the QAT.

The third method is to switch manually to play mode (click the Play button in the sidebar) and click the “New Game” button in the “Home – Play” tab. This immediately starts a game using the current defaults. You can also select “Start from Position” if you want to set up the starting position of the game instead of starting from the initial position. As you can see, the “Resign” and “Stop Game” buttons can also be found on this tab.

Start a new game.

	If you are examining a database game or a game in the Sandbox, you can click the “Play this game” action link in the sidebar.
		Start play from database game.

What happens here is that the current game is copied to play mode up to the current position and you can start playing from there. It doesn’t matter if it’s a mainline position or one of the variations. When you start a game in this way, you are first asked about the time control you want to use and after that you can make your first move. You may also want the engine to make the first move. In that case click the “Force Move” button in the “Home – Play” tab on the ribbon.

The Game Control group.

Besides the “Force Move” button, the “Game Control” group contains the “Take Back” button, “Switch Sides” and the “Show Analysis” options. The first two buttons should be familiar to anyone who has played against the computer. The third one controls whether you see the engine’s analysis and the opening book while playing.

The Game Options

So far we have only seen how you can play a game using whatever settings may be in effect when you start the game. Now we will examine how you can access the most common settings, such as the engine to play against, the time controls, which side you play, handicaps, hints and other assistance, etc.

	The sidebar gives you a quick overview of the current settings, as you can see in the following image. You can click the blue underlined links to change the settings. At the top left you can see that Lisa is playing and we saw how you can switch to a different profile or create new ones. Delfi is a chess engine that comes with Aquarium. If you click the engine link you will get a list of all installed chess engines and can select a new opponent. The “Time Control” field shows that we will be playing a five minute game. Clicking the link allows you to select any time control you like. We have a closer look at the time control options later in this article. “Color” is set to “Automatic”, which means that you will switch sides after each game. If you click the link it cycles between “White”, “Black”, and “Automatic”.
		Quick settings.

“Handicap” is set to “No handicap.” This means that the engine will play at full strength and without material handicap. Clicking the link brings up a dialog box where you can select a variety of strength and material handicaps. We will have a detailed look at the handicap options below.

Finally, the engine rating is displayed, and you can see that Delfi’s rating is 2500.

After choosing the setting you prefer, you can start playing by clicking “New Game”.

	Getting Help If you are playing in fun mode (see the icon on the left in the illustration below), you can ask Aquarium for help while you are playing.
Fun mode and tournament mode.

The icon on the right is shown in the ribbon when you are playing in tournament mode. Tournament mode doesn’t allow any assistance while playing. You can switch between fun mode and tournament mode by clicking the icon, but you can’t switch the game to tournament mode after getting a hint or other help during the game. If you are playing in tournament mode and ask for assistance you are given a warning that it will require switching to fun mode.

	Assuming that you are playing in fun mode you can use the tools shown in the following image to get hints and other help while playing. If you click the Assist button, Aquarium shows the move that the engine recommends. If you click the small black triangle on the button, the following menu is displayed.
		Get assistance while playing.

Hint is equivalent to clicking Assist and shows the recommended move. Several Best Moves displays one or more green arrows showing the top candidate moves. Show Opponent’s Intention shows you what the engine is threatening, i.e. what it would do if it could move immediately again. The “Make Move” button makes the move recommended by the engine. You can use this button if you are not sure what to do next and want the engine to decide instead. Usually, you would do that after using the “Hint” button to see the move recommended by the engine.

The “Options” button opens a dialog box where you can tell Aquarium to watch your play and warn you if you play bad moves. It also defines how long the engine should search when you ask it for hints.

Here we see that “Warn about blunders” is selected, so Aquarium will let you know when you blunder and give you a chance to select a better move. “Blunder threshold” is set to 100 centipawns. It means that you are not warned unless the blunder is equivalent to losing a pawn or more. The percentage below the threshold says that a warning will not be issued unless the blunder decreases your winning chances by at least 2%. This focuses the warnings on the more interesting parts of the game. If you are completely lost, then dropping a pawn has no effect on the outcome of the game, so it would not be reported with the settings shown above. “Hint time” is set to two seconds, which means that the engine will base its hints on a two second search. Set these parameters to whatever you feel is appropriate based on the speed of your computer and your chess strength.

Handicap Settings We already saw that you can access the handicap settings from the sidebar by clicking the “Handicap” link. They are also accessible from the ribbon as shown below.

	Clicking the “Handicap” button brings up the handicap dialog box. There are radio buttons at the top of the dialog where you can select “None” when the engine will play at full strength, “Skill” for selecting rating handicaps and “Material” for material handicaps. Here we see the rating handicaps. The “Skill Settings” pane allows you to select from three different methods: Special engine (700-1900). Here Aquarium will always use a special rating handicap engine. It accepts a rating range from 700- 1900. Multivariation mode (1200-2400). The engine is run in multivariation mode and Aquarium picks one of the moves to play. The lower the rating, the more likely it is that a low-ranking move will be picked. Engine based (1200-2400). This method is only effective when you are playing against Rybka and uses its own internal handicap method.
		Three types of rating handicaps.

You may ask yourself which of these three methods is best. The answer is that if there was a proven best method, then there would be no reason to offer more than one. Play a few games and see which one you like best. Some may like to switch between these methods for variety as they produce very different games.

After you pick the handicap method, use the slider at the bottom of the dialog to select the rating level. Just remember what I said earlier about rating levels! Experiment and find a rating that makes you enjoy playing against the engine. That’s what matters.

If you select “Material” in the “Handicap” pane, Aquarium will display a list of available handicaps. They are categorized according to difficulty, from a pawn handicap to queen and two rooks. First you pick the category and in this case I have chosen the “Very Hard” category. I have clicked on a knight handicap and the diagram shows the initial position without the knight on b1. I might want to start the game without the knight on g1 instead. In that case all I need to do is click the “Next position” button below the board and Aquarium will remove the knight on g1 instead of b1. In general, the “Next position” button cycles between all available positions of the type you have chosen.

Material handicaps.

	Note the label at the top of the diagram. It says “Human” and marks the side that you will play; the black side in this case. But what if you wanted the engine to play the black side without the b8 knight? Traditionally, that is called “knight and move” and it is actually one of the options you can choose as shown in the next screenshot. After selecting the handicap, click OK and start the game.
		Knight and move handicap.

Time Handicaps Clicking the “Time Control” link in the sidebar displays the following dialog box. In order to set up a time handicap, make sure that “Same time for both players” is not selected. After that you can set the time for each side as you like. Set your time control in the “Player” pane and the engine’s time control in the “Engine” pane. In this case I have selected fifteen minutes and a five second increment after each move for myself. The poor engine only gets one minute for the whole game and no increment. Besides decreasing the strength of the engine, it speeds up the game as the engine will reply almost instantly. Of course I can combine the time handicap with a rating handicap (and even material handicap) to reduce the strength of the engine even further.

Time handicaps.

	We’ll have a look at two more examples. Here we are looking at a time per move time control.
		Time per move handicap.

	In this case I give myself five seconds for each move, but the engine only gets one second. In the third example we are looking at a fixed depth engine handicap. Of course there is no corresponding setting for the human player, so you only need to set a limit on the engine. Here I have chosen a very low depth, but even then Rybka can play a fairly strong game.
Fixed depth engine handicap.

The New Game Options If you want to access all the play options before starting a game, you can do so by selecting “Options” from the drop-down menu on the “New Game” button. Here we see that besides the new game options you can also choose to play a FischerRandom or a Chess960 game against the engine. In that case you can also apply the rating, time and depth handicaps described above.

If you select “Options,” you’ll see the following dialog box. I’m only showing the left half, but the right half allows you to set the time controls for the game. The “Event” field is automatically assigned by Aquarium and gives the “event” a name, but you can overwrite it with your own description. Instead of normal text you can also use variables, like those that Aquarium uses in the default string. The “Edit name” button (not visible in the image) shows the meaning of the variables. We have already covered “Player Color” (White, Black, Automatic), “Preferred Mode” (Tournament, Fun) and you choose the engine to play against in the “Engine name” list. If a chess engine gets into a lost position, it plays on until it is checkmated, while a human player resigns when he feels that continuing the game is pointless. You can force the engine to behave in a similar way. First, select “Resign if score is above” and then the evaluation difference (in pawns) that indicates a lost game. In this example I have selected five pawns. This means that the engine will resign if it finds itself five pawns or more behind for three successive moves.

New game options.

If you select “Ponder”, the engine will also think on your time. This is sometimes called “permanent brain”. The “Handicap” button displays the handicap dialog box that we examined above.

Finally, you can decide if loss on time is only flagged for the engine, for both players or not at all. If you select “For computer only” as in this example, you can ignore your own time control and take as much time as you like for your moves.

By the way, if you are looking forward to the new Aquarium version my crystal ball tells me that it will be available before the end of the month. It will be free for current Aquarium users.

Dadi Jonsson.