Release Notes

Update released on February, 12th 2021

  • Video support
    • There is now a YouTube channel. You can find a link to it on the front page.
    • The first videos are explanations of new features (see below).
    • are working on a chess related YouTube video search.
      We queried their database, and can now show matching videos for some of our puzzles.
      There is a list with these puzzles here:
      This is an experiment, please let us know if this is interesting.
  • New levels - play like a champion
    • There are twenty new levels 41 to 60, in a new chapter "Play like a champion".
    • Each level contains puzzles based on games of a famous player. You take their side and must find the winning moves that they played.
    • The first two levels "Vladimir Fedoseev" and "Wesley So" are unlocked.
    • Score eight or more to unlock the next level.
    • Unlock all levels to play like world champion Magnus Carlsen in level 60.
  • Chess terms explained: Some of the text annotations on the solution page now have a pop up with an explanation of chess terms.
  • Video showing the new features:

Update released on January, 31st 2021

  • Annotated puzzle solutions
    • On the solution page, text and graphical annotations are now shown for the following tactical motifs:
      • Fork
      • Pin
      • Skewer
      • Discovered attack
      • Discovered check
      • Capture defender
      • Trapped piece
      • Attacking a pinned piece
      • Decoy
      • Deflection
      • Double check
      • Unpinning
      • Clearance
    • Text annotations are in English. Support for more languages is planned.
    • When you replay the annotated move, graphical annotations in the form of arrows is displayed.
    • All puzzles used in levels 4 - 20 (except level 16) are now showing annotations.
    • Support for more motifs and puzzles is planned.
    • Video with some examples:

Update released on January, 27th 2021

  • The website is now available in French.
  • Increased the server and database capacity.
  • Performance improvements.
  • Puzzles with task "regain material" are now labelled as experimental.

Update released on January, 4th 2021

  • The filter now has a separate selection for the checkmate pattern, if you select Win/Checkmate.
    The checkmatte patterns introduced with the levels can now also be selected from this filter.
  • Refreshed levels 1 to 20.
    These are now based on 17116 puzzles (up from 4003).
    Replay a level with different puzzles to master the most important tactical motifs.
  • All defence puzzles now show a threat in the solution view. Some of them show multiple threats.
    All defence puzzles were recalculated with the new rules.
  • Updated Spanish, Turkish, and German translations.
  • Implemented features for resending confirmation mails, and changing the email address of accounts.
    You can find these in your user profile.
    Confirming your email address is important - in case you forget your password, this allows a password reset.

Update released on December 15th, 2020

  • New levels:
    • There are twenty new levels for learning checkmate patterns.
    • On the levels page, click on "Checkmate patterns" to switch to levels 21 to 40.
    • The first two checkmate pattern levels are unlocked. Solve at least eight out of ten to unlock the next level.
    • The difficulty increases during each level.
    • Replay any level to get different puzzles with the same checkmate pattern.

Update released on December 9th, 2020

  • Improvements to lists:
    • The author of a list can now delete a list, and rename a list. These options are available on the lists page after selecting the list from the drop down.
    • Bug fix: Long lists can now be replayed.
      However progress of these replays isn't stored permanently, so you can't resume a replay of a long list later.
      Replay and resume will be added later.
  • Improvements to levels:
    • Fixed a bug where sometimes a level wouldn't start correctly.

Update released on December 3rd, 2020

  • Improvements to levels:
    • The images on the level selection and level completed screens are now using the chess board and pieces selected in the user settings.
    • The level completed screen now works better on some laptop screens.
    • Added a button "Next level" to the level completed screen.

Update released on November 30th, 2020

  • Improvements to rating system:
    • Starting last year, new features were introduced that destabilized the rating system.
      This includes the levels, and the motif filter.
      Solving a puzzle with these hints is considerably easier, 127 Elo points on average.
    • Each puzzle now has a separate "hint" rating.
    • The hint rating is used, when you received a hint while solving a puzzle.
    • Currently, this includes playing a level, and selecting a motif or sub-task from the filter.
    • All player and puzzle ratings were adjusted by 200 points to compensate for the rating decline.
      Ratings of puzzles that are part of a level were adjusted by an additional 127 points.
    • Ratings should now more closely match existing rating system such as FIDE Elos.

Update released on November 25th, 2020

  • Updated the contact page with new email addresses.
  • Fixed a performance issue when playing some puzzle lists.
  • Improved performance of some pages.

Update released on November 20th, 2020

  • Fixed some layout issues.
  • Fixed an issue on the Patron page when the language was set to German.
  • Fixed an issue where the "Take back" button was not accessible by keyboard.
  • Fixed an issue where no error message was displayed when trying to create a new puzzle list without entering a name.

Update released on November 18th, 2020

  • Improved user experience when puzzle completed
    • Moved the information displayed when a puzzle is completed into a panel.
    • On mobile devices, this panel is shown as a modal popup without requiring scrolling.
  • Improved the display of modal popups in dark mode.

Update released on November 10th, 2020

  • Puzzles with the task "checkmate" are no longer considered experimental and are now included in the default selection.
  • Improvements to puzzle generation algorithm:
    • Added some puzzles with two options on the 2nd move.
    • Extended some puzzles with only two good moves in the end position.
    • This allows puzzles, where two moves can be played in either order but are otherwise forced.
    • This improves some endgame puzzles, where the King can go on a route via two different squares.
    • This improves some defend puzzles, where the defender has limited options available.

Update released on November 5th, 2020

  • If you become a patron, you can now enjoy an ad-free site.
  • The players list now has a search box.

Udpate released on October 30th, 2020

  • The month can now be selected on the leaderboard page.

Update released on October 29th, 2020

  • Additional players were added to the players list.
  • The players list now has some checkboxes for filtering the players:
    • World Champions
    • Candidates
    • Female
    • Women's World Champions
  • A little retconning of chess history was required to make it fit into these checkboxes.
    For "World Champion" I consider the matches Kasparov - Short 1993, Kasparov - Anand 1995, Kasparov - Kramnik 2000, Kramnik - Leko 2004, Kramnik - Topalov 2006 as legit, and also the round robin tournaments 2005 in Argentina, and 2007 in Mexico.
    The FIDE world championship tournaments in KO format 1998, 1999, 2000, and 2002 I am retconning as World Cups, with Anand the winner in 1998.
    Therefore the world champions are Kasparov, Kramnik, Topalov, Anand, Carlsen.
    For "candidates" I've included all vice world champions, before candidates tournaments were introduced. If there was a round robin final, I've included the finalists.
    This is my personal view of chess history, your mileage may vary.
    Also note that not all candidates and female world champions have enough puzzles yet to be listed here. They'll be added, when there are enough puzzles.

Update released on October 25th, 2020

  • Show your own score on the leader board, if you are not in the top 10.
  • Improvements to dark mode on leader board and user profile pages.

Update released on October 24th, 2020

  • Leaderboards:
    • Leaderboards are now live.
    • To participate in the leaderboards, go to your user profile and check the option "Participate in leader boards".
    • There is a new main menu entry for the leaderboards.
    • There are four different types of leaderboard:
      • Number of attempts
      • Accuracy
      • Rating
      • Rating change
    • You can switch the leader board types by clicking the column headers. Some conditions apply to each leader board, for example you need at least 25% accuracy to be shown on the leaderboard for number of attempts. These conditions are listed below the leaderboard.
    • Leaderboards will reset each month. The rating doesn't reset, it will be the best rating at the end of the month that counts for the final standings.
  • The main menu entry for contact has been removed. This can now be found on the About page.

Update released on October 21st, 2020

  • Leaderboards:
    • Leaderboards will be available soon.
    • To participate in the leaderboards, go to your user profile and check the option "Participate in leader boards".

Update released on October 11th, 2020

  • Improvements to defence puzzles:
    • In some defence puzzles you can now see the threat on the solution page.
    • This is currently being tested, and calculated for all defence puzzles.
    • If you want to try this, there is a list "Updated defend puzzles" on the lists page.
  • The website is now available in Romanian.
  • Featuring 30 additional players on the players page.
  • Better support for the user profile on mobile devices.

Update released on October 7th, 2020

  • Showing monthly progress on user profile.

Update released on October 3rd, 2020

  • You can now support and become a patron.
  • Highlight squares and draw arrows:
    • Use the right mouse button and click a square to highlight it.
    • Use the right mouse button, click and hold, and release on another square to draw an arrow.
    • Hold CTRL while clicking to get a yellow highlight or arrow.
    • Hold ALT while clicking to get a blue highlight or arrow.
    • Hold CTRL and ALT while clicking to get a green highlight or arrow.
    • Left click or move to remove the highlights.
  • Play long lists:
    • You can now play lists with more than ten puzzles.
    • If you are logged in, you can resume the progress on another day.
    • This is useful for lists with many puzzles, like the list of all daily puzzles with more than 1.000 puzzles already.

Update released on September 18th, 2020

  • The filter now includes the following additional motifs:
    • Double check
    • Knight / Queen / Rook / Bishop / Pawn fork
    • Knight / Queen / Rook / Bishop / Pawn sacrifice
    • Mate with Queen / Rook / Bishop / Knight
    • Mating net
    • Block escape square
    • Weak backrank
    • Mating patterns:
      • Anastasia's mate
      • Arabian mate
      • Kiss of death
      • Dovetail mate
      • Smothered mate
      • Swallow's tail mate
    • Deflection into promotion / checkmate / capture / check / skewer / fork
    • Decoy into checkmate / pin / skewer / fork / discovered attack

Update released on September 15th, 2020

  • Removed the "beta" tag.
    • Puzzle types that are new or still being researched have been marked as "experimental" over the last couple of updates.
      They are no longer part of the main experience (without filter).
      The error rate of the main algorithm is now so low, that the "beta" designation can be removed.
    • The "checkmate" puzzles already are quite popular. They will be moved to the main experience when the error rate has gone down a bit more.
    • The "defend" puzzles remain experimental until further improvements have been completed and tested.
  • While promoting, the unpromoted pawn is now displayed correctly centered on the promotion square.
  • Fixed a bug where some puzzles with the new "checkmate" task would end before checkmate.

Update released on September 9th, 2020

  • Improvements to solution view:
    • Improved layout on small screens such as mobile phones.
    • When replaying the solution or game, moves are now animated.
    • The move list automatically scrolls when replaying a long game or solution.
    • When making a move on the analysis board, sound is now enabled.
    • An evaluation bar is now shown when turning on engine analysis.
    • Improved keyboard support.
    • Fixed a bug, where some piece sets were not displayed correctly in the solution view.
  • New "checkmate" task:
    • There is a new puzzle task "checkmate".
    • In these puzzles there might be several ways to win the game, however there is only one way to checkmate quickly.
    • In order to solve a "checkmate" puzzle you have to checkmate your opponent. Winning material is not enough.
    • These puzzles are experimental for now. You can play them using the filter, by either selecting "Any task (include experimental tasks)" or "Win / Checkmate".

Update released on August 18th, 2020

  • "Defend" puzzles:
    • Some of these puzzles can be difficult to understand.
    • Improvements are planned for these puzzles.
    • In preparation of these improvements, they have now been marked as "experimental", and are not shown to users by default.
    • In the filter, you can still select the "Defend" task, or select the new option "Any task (include experimental tasks)" to continue playing defend puzzles.
  • "Defend and win" puzzles:
    • In some puzzles, the solver starts with a winning material advantage, and has to win.
    • In these puzzles, the solver has to defend against threats of the opponent, such as checkmate, perpetual check, regaining material, etc.
    • After having defended against these threats, the puzzle ends, as the material advantage is then sufficient to win.
    • The planned improvements for "Defend" puzzles apply to these puzzles as well. Therefore, the task of these puzzles is now "Defend and win", and they have been marked experimental, too.
    • There is a new option for these puzzles in the filter.

Update released on August 13th, 2020

  • Fixed a bug where sometimes the move numbers in the notation weren't shown correctly when using the new option to show the last opponent's move.

Update released on August 7th, 2020

  • The website is now available in Spanish.
  • Showing the last move of the opponent:
    • Added a new option to show the last move of the opponent at the start of the puzzle (turned off by default).
    • Added a new option to show the last move of the opponent at the start of defend puzzles (turned on by default).
  • Improvements for levels and lists:
    • Clicking any puzzle on the lists page now starts playing the list.
    • The progressbar items for levels and lists now show a small diagram of the corresponding puzzle when hovering over it. Clicking the progressbar item navigates to the solution of the corresponding puzzle.
    • Added new artwork to the list completed screen.
  • Clicking any puzzle on the player page now sets the filter to this player.
  • Added a sub-menu on the user name in the main menu for logged in users, containing the "User profile" and "Log off" items.
  • Updated logos, including maskable versions for the PWA.
  • A warning is displayed, if the website is accessed with a very old browser, such as Internet Explorer.
  • Improved layout of the About page.
  • Fixed an issue with displaying the solution of puzzles based on game fragments.
  • Fixed an issue with displaying the main line of the solution of some complicated puzzles.
  • Fixed an issue with the display of dates with Arabic language selected.

Update released on July 5th, 2020

  • Better support for iOS devices
  • Improved layout shift
  • Performance improvements
  • Improved PWA support on Apple devices
  • Fixed a layout issue on mobile phones with Arabic language selected.

Update released on June 18th, 2020

  • Sound effects should now work properly in Safari browser on Apple devices.

Update released on June 14th, 2020

  • Better support for high dpi devices
  • Basic keyboard support:
    • Navigating the website with the keyboard is now supported, and keyboard focus indicators are displayed.
    • Keyboard support when solving a puzzle:
    • Use cursor keys, "A" to "H", "1" to "8" to move the cursor to a square.
    • Use "Enter" to select a square.
    • Select start and destination square to make a move.
    • Select a promotion piece by pressing "1" to "4".

Update released on June 10th, 2020

  • Opponent moves are now animated.
  • Added sound effects for moves.
  • Settings: New option for selecting the type of sound effects (select "Wood" or "Arcade"), and turning them off (select "None").
  • Settings: New option for turning the animations on or off.

Update released on May 28th, 2020

  • The website is now available in Croatian.
  • The chess board now supports moving a piece by clicking the start and destination square, in addition to dragging the piece.

Update released on May 19th, 2020

  • The website is now available in Portuguese.
  • The chess diagrams visible on the homepage, player page, and lists page are now faster and support the different piece sets and board styles from the settings.

Update released on May 9th, 2020

  • The website is now available in Japanese.
  • Dark mode is supported and can be selected in the settings.

Update released on April 27th, 2020

  • The website is now available in Arabic.
  • An offer to switch languages is shown when viewing a page in a language different from the one selected in the browser.
  • Added several new players to the list of famous players.

Update released on April 24th, 2020

  • The website is now available in Chinese and Hindi. Use the settings menu to switch the language.
  • The website is now available as a PWA (progressive web application).
    You can install it on most devices.
  • Basic offline support:
    An offline page is displayed when navigating without connection.
    An error message is displayed when making a move when disconnected. The move can be retried again.

Update released on April 15th, 2020

  • The website is now available in Dutch and Finnish. Use the settings menu to switch the language.

Update released on April 9th, 2020

  • The website is now available in Russian. Use the settings menu to switch the language.
  • Added an option to show last move arrows to the settings.

Update released on March 29th, 2020

  • The website is now available in Turkish. Use the settings menu to switch the language.
  • Added mouse wheel support to play through games or solution in the solution view.
  • Added a volume control to the settings to allow changing the volume of the sound effects when you play a level or list.

Update released on March 17th, 2020

  • Improved puzzle generation algorithm by cutting trivial recaptures at the start of puzzles.
    About 1000 puzzles now start with a more interesting position.
    About 9000 puzzles with the "regain material" task were deleted, improving the quality of this type of puzzles.
  • Fixed a bug with black castling rights in the analysis board in solution view when entering your own moves.
  • Added several new players to the list of famous players.

Update released on February 28th, 2020

  • The website is now available in German. Use the settings menu to switch the language.

Update released on January 20th, 2020

  • Improvements to some difficult puzzles and some endgame puzzles.

Update released on January 12th, 2020

  • The list of players now has images.

Update released on January 1st, 2020

  • Added a settings dialog which allows to customize the puzzle solving UI.
  • This includes different piece sets, boards, and the option to show or hide the task and meta data while solving puzzles.
  • These settings are stored per device, so you can set different options on your PC, tablet and smart phone.
  • You can now play a list. Select a list on the lists page, and press the play button, to play 10 puzzles from the selected list. If the list has more than 10 puzzles, the selection is randomized, so you can replay with different puzzles.

Update released on December 22nd, 2019

  • Fixed a bug where the "Log in" menu item wasn't correctly rendered on some screens.

Update released on December 16th, 2019

  • Fixed a bug where a level didn't correctly unlock after completing several levels in a row.

Update released on December 13th, 2019

  • Fixed a bug where a puzzle wasn't saved correctly to a new list.
  • The save button is now also available on the solution screen.
  • Fixed a bug where the level indicator was shown incorrectly when solving a different puzzle while playing a level.
  • Improved sound effects when playing a level.

Update released on December 11th, 2019

  • There are now twenty levels, where you can learn tactical motifs. The puzzles contained in a level are selected to include only the motif being trained. A level always consists of 10 puzzles, but you can replay a level and get different puzzles with the same motif.
  • You can now save a puzzle to a list by using the save button. This feature requires registration. There are also a number of automatic lists, where you can see all puzzles you played, all puzzles you liked, etc.
  • The navigation at the top now has additional menu items for Lists, Levels, and Players.

Update released on November, 1st 2019

  • Fixed some bugs with reply move generation, where some weird moves were played by the opponent. Reply move generation is also a bit more greedy than before.
  • In positions with a complicated mate, alternate solutions are now allowed without triggering "There is a better move". For example, if there is a mate in 12, you are now allowed to play a mate in 15. "There is a better move" is still shown for easy mates, for example if the position is mate in 1, and you select a mate in 2, "There is a better move" is shown. This is to limit solution trees in puzzles where the winning player can sometimes postpone mate for many moves.
  • All existing puzzles were recalculated with these changes.

Update released on September, 12th, 2019

  • This year, usage of the site has grown a lot. Thank you!
    In order to be able to keep available for free, there is now some advertising.
    While you solve a puzzle, there are no ads. No distractions while you concentrate.
  • Added 50 more chess players to the list of famous players.
  • Updates to the filter:
    • The filter has a new option to select an opening variation, to get puzzles relevant to the selected opening.
    • The difficulty filter is now using a slider control, which should be more convenient than entering a number.
    • There is a "reset to defaults" button.

Update released on August, 20th, 2019

  • Fixed a bug where "there is a better move" was not shown correctly in some draw puzzles.

Update released on August, 16th, 2019

  • The filter is extended with additional motifs:
    • Double attack
    • Discovered check
    • Discovered attack
    • Trapped piece
    • Unpinning
    • Attacking pinned piece
    • Clearance
    • Decoy
    • Deflection
    • Intermediate check
    • Desperado
  • To give easier access to the filter, and to make it more popular, there is now a filter button next to the next puzzle button.

Update released on June, 15th, 2019

  • In draw puzzles, if a position is repeated, a different reply move can now be selected by the opponent. This makes some draw puzzles more challenging:
    • In some endgame positions that are theoretically drawn, the opponent is now much less likely to agree to a repetition of moves.
    • In some puzzles that end in perpetual check, the opponent will now try different moves to escape the perpetual.
  • In positions where the player gains material, the opponent will no longer sacrifice additional material just to prolong the puzzle.
  • All puzzles were recalculated with these updates.
  • The filter now has additional options when checkmate is selected: Mate in 1, mate in 2, ..., mate in 5, mate in more than 5.
  • The filter now has a new option to select a motif. The following motifs are available in the first version of the motif filter:
    • Fork
    • Pin
    • Skewer
    • Sacrifice

Update released on April, 20th, 2019

  • Puzzles that were labeled "draw or win" have now been split into two separate tasks, "regain material", and "defend".
  • The filter has been extended with two new tasks:
  • Winning puzzles can now be filtered further for "checkmate" and "material gain".
  • Drawing puzzles can now be filtered further for "stalemate", "repetition", and "insufficient material".
  • If you select a combination of filters with few or no matching puzzles, and you have solved all of them, you are returned to the filter with a warning message.

Update released on March, 10th, 2019

  • Fixed a bug where some puzzles were published before they were completed.

Update released on January, 13th, 2019

  • Added player pages.

Update released on January, 8th, 2019

  • Added filter by player.

Update released on October, 11th, 2018

  • Fixed a bug with some stalemate puzzles.

Update released on October, 8th, 2018

  • Added filter by task.

Update released on August, 12th, 2018

  • Fixed a bug where some positions were not correctly labeled with "there is a better move".

Update released on June, 16th, 2018

  • In positions with a forced mate, allow alternate solutions if they are quicker. For example, capturing the Queen is now allowed as a solution in a position where the best move is a long complicated mate.

Update released on May, 5th, 2018

  • Chess tournaments can now be featured on the daily puzzle.
  • Fixed a bug where some puzzles without a solution were published in error.

Update released on April 13th, 2018

  • Fixed a bug where "there is a better move" was shown for the best move, which made it impossible to solve some puzzles.

Update released on August 16th, 2017

  • Homepage updated with dynamic lists of puzzles.

Update released on August 10th, 2017

  • Puzzle solving
    • When promoting, you can now select the promotion piece, instead of auto-queen. Puzzles that require an under-promotion can now be solved correctly.
    • Puzzles that always end with perpetual check, move repetition, stalemate, or insufficient mating material, are now labeled as "to draw", instead of "to draw or win". Puzzles that end with an equal or slightly better position are still labeled as "to draw or win" as before.
  • Solution display
    • The browser engine was upgraded to Stockfish.js 8.
    • Engine evaluations are now always displayed from White's point of view.
    • Engine evaulations are now displayed with an added symbol ("+-", etc.)
    • The solution variation now always starts with the last move before the puzzle. This enables correctly displaying the solution variation if the puzzle is at the end of a game.
    • The solution variation is now preselected. This means that if you use the replay buttons, the solution will be replayed, which is a better experience, especially on mobile.
    • On mobile, the buttons and engine are now displayed before the notation, which makes the engine usable on many mobile devices without scrolling.
  • Puzzle generation
    • Puzzles where the result depends on the 50 moves rule are no longer generated.
    • Puzzles do no longer end if a winning condition is reached, but the next move is still forced.
    • Fixed a bug that caused the generation of some puzzles that had no solution.
    • Fixed several bugs with the generation of reply moves.
    • Improved detection of reply moves that would lose material.
    • Improved generation of reply moves in table base positions.
    • All puzzles were recalculated to fix these issues in existing puzzles. Some puzzles are no longer available.