Pandemic: a new fairy condition (Alexandre Leroux)

Pandemic: a new fairy condition

by Alexandre Leroux

(→ PDF version of the Article)

Original problems included:
No.1503.1-3 – Alexandre Leroux (Canada)
No.1503.4 – François Labelle (Canada)

Original Retro & PG problems
JF – R2019-20

In order to alleviate the boredom associated with the current COVID-19 pandemic,
I propose the creation of a new fairy condition called “Pandemic”.


Rule #1: Contagion

When a black piece moves, all the white pieces adjacent to its destination square become black.

Rule #2: Distancing

White can only move a piece if its destination square is not adjacent to any black piece.

The white King is not affected by these two rules.

The Pandemic condition is deliberately asymmetrical. It simulates the fact that COVID-19 (Black) is spreading rapidly (contagion rule), while humanity (White) is strongly restricted in its movements (distancing rule). Finally, the white King, who is immune to both pandemic rules, simulates a government trying to defeat COVID-19. The following problem illustrates the condition.

No. 1 Alexandre Leroux

Solution: (click to show/hide)

white Ke1 Qd1 Ra1h1 Bc1f1 Sb1g1 Pa2b2c2d2e2f2g2h2 black Ke8 Qd8 Ra8h8 Bc8f8 Sb8g8 Pa7b7c7d7e7f7g7h7

Proof Game in 7.0 moves (15 + 15) C+

In this example, we can deduce that the Bishop on c3 was white and was “contaminated” by the black Rook on the last move, otherwise the check would be impossible. So White had to capture the missing black Pawn and Bishop, but to do so, these two pieces must first be isolated. Moreover, White must lose a tempo, because e2-e4 would prevent e5 from being played without contaminating e4. This problem illustrates the fact that checks are not orthodox with the Pandemic condition. For example, in this problem, when the black King goes to f8, he is not put in check by the white Bishop on b4. The white Bishop may not capture the black King, because the Bishop would become adjacent to a black piece, which is forbidden by the distancing rule. The first problem illustrates how easy it is for the pandemic to defeat humanity. Note that White is checkmate on the diagram: it is impossible to capture the black Bishop or to interpose a white piece without violating the distancing rule. It quickly becomes clear that COVID-19 has a serious advantage!

On the other hand, it is very difficult for humanity to defeat the pandemic, as illustrated by the following two problems. Can you find the single move by White that checkmates Black in each case?

No. 2 Alexandre Leroux

Solution: (click to show/hide)

white Kf7 Qh1 Rc2c4 Bc1d1 Sf1c6 Pc7 black Kf5 Bb1 Sa8

#1                                           (9 + 3) C+

No. 3 Alexandre Leroux

Solution: (click to show/hide)

white Kd1 Qc1f1a2g3a5g6b7e7 black Kd4 Rh8 Pa3

#1                                           (9 + 3) C+


In the definition of the Pandemic condition, the term “adjacent” includes orthogonal and diagonal squares, so up to 8 squares can be contaminated by a single black move! The white King (or any other Royal white piece) cannot be transformed and acts like an orthodox King. Castling is considered a King move, so the Rook is not affected by the distancing rule when White castles. In the case of Black, the King cannot castle out of check or if the King would be in check on the Rook’s end square. However, the King is never in check on the castling end square, because the Rook protects him by the distancing rule (see No. 7). Finally, it is allowed to castle with a white Rook transformed into black on a8 or h8, if the newly transformed Rook has never moved. The following problem illustrates some of the subtleties of the condition.

No. 4 Alexandre Leroux
Original 1503.1

Solution: (click to show/hide)

white Ke1 Ra1h1 Bg5 Pf2e2g3 black Ke8 Ra8h8 Bh6 Pa7c6e6b7d7

Which castlings are possible? (7 + 9)


I propose three variants to the Pandemic condition that could make the job easier for White. The first, “Pandemic with orthodox checks”, prevents the black King from protecting himself from check by being adjacent to a black piece. Normal checking rules apply to both sides. The second, “Pandemic without distancing”, applies only the rule of contagion, which allows White more freedom of movement. Finally, “Pandemic Rex Inclusiv” removes all exceptions for the white King (or any other Royal white piece). Since this can result in a position with two black Kings, the author should specify if Siamese Kings, Royal Dynasty, Rex Multiplex (or other) rules are applied. The Pandemic condition could also be combined with many other fairy conditions for interesting effects, such as “Non Royal Kings”. With this fairy condition, the King becomes a normal piece as in “Losing Chess”. Checks and castling disappear, and it becomes possible to make a promotion to King. The following problem illustrates how the pandemic can spread to the whole chessboard by adding this condition.

No. 5 Alexandre Leroux
Original 1503.2

Solution: (click to show/hide)

white Ke1 Qd1 Ra1h1 Bc1f1 Sb1g1 Pa2b2c2d2e2f2g2h2 black Ke8 Qd8 Ra8h8 Bc8f8 Sb8g8 Pa7b7c7d7e7f7g7h7

Proof Game in 6.0 moves (0 + 32) C+
Non Royal Kings

In conclusion, I hope that this condition will inspire composers and allow solvers to take their mind off daily concerns. I thank François Labelle, the creator of the fairy chess helpgame solver Jacobi, who has been kind enough to add this condition in his program. To finish on a note of hope, the two following problems show that it is possible to checkmate COVID-19 in only 13.5 moves, and to completely wipe it out in 15.5 moves!

No. 6 Alexandre Leroux
Original 1503.3

Solution: (click to show/hide)

white Ke1 Qd1 Ra1h1 Bc1f1 Sb1g1 Pa2b2c2d2e2f2g2h2 black Ke8 Qd8 Ra8h8 Bc8f8 Sb8g8 Pa7b7c7d7e7f7g7h7

Proof Game in 13.5 moves (9 + 16) C?

No. 7 François Labelle
Original 1503.4

Solution: (click to show/hide)

white Ke1 Qd1 Ra1h1 Bc1f1 Sb1g1 Pa2b2c2d2e2f2g2h2 black Ke8 Qd8 Ra8h8 Bc8f8 Sb8g8 Pa7b7c7d7e7f7g7h7

Proof Game in 15.5 moves (16 + 1) C+

10 Responses to Pandemic: a new fairy condition (Alexandre Leroux)

  1. Mario Parrinello says:

    Dear Alexandre e François, I’m doctor and I’m sure you understand to what extent I understand the present sad pandemic situation, hence thanks so much for presenting this very interesting fairy condition.
    It seems very promising and of course very suitable for PG and retro as you have already shown in your article.
    But what about for help stipulation? In this regard I would have wished that also the contagion and and distancing rules would have been reversed in order to allow both Black and White to exploit both properties. What do you think? Thanks.

  2. Vlaicu Crisan says:

    Mario, what you suggest is no longer Pandemic – it’s either Vaccination or Immunisation! 😊

  3. Mario Parrinello says:

    Vlaicu, thanks for your remark that gives me the opportunity to explain better what I mean, sorry for not being very clear.
    I’m suggesting to apply the rule#1 (Contagion) to black pieces (when a white piece moves, all the black pieces adjacent to its destination square become black), and the rule#2 (Distancing) (Black can only move a piece if its destination square is not adjacent to any white piece ).
    We all are waiting for an effective vaccine against coronavirus but not against Pandemic condition!

  4. Alexandre Leroux says:

    Dear Mario,

    Indeed, right now in help conditions Covid (Black) must be mated, which is a bit hard. If you want Humanity (White) to be mated (which is very easy), perhaps one could simply write “H#X – White to play”, which would imply that White is mated if X is an integer? I’m not sure if this contradicts existing helpmate rules. Alternatively, perhaps I could add a variant called “Pandemic – Reverse colors”, or something similar? This would allow the “H#” objective to stay the same as usual, but now Humanity is Black and must be mated. On the other hand, if you want both sides to be symmetrical, so that both sides have a contagion and distancing rule, it would need another Variant such as “Pandemic – Humanity fights back” or something like that with a better name haha. Interestingly, someone also suggested to add a “Vaccination” rule. All these new variants could be added in a future article or update!

  5. Nicolas Dupontdupont says:

    If I understand, Mario would like to get an “inverted colors” variation of the Pandemic condition, which looks more suitable for helpmates where the black king is checkmated. Indeed in the Pandemic condition, the “natural” king to be checkmated is the white one, as illustrated by example 1.

  6. Alexandre Leroux says:

    Yes, “Pandemic – Inverted colors” is a very good idea and would be an easy variant to add in my next update! For Helpmates and similar stipulations, this can be tested in Jacobi by selecting “First Move Override –> White to play”. This might be noted “h#x – White to play” or “h#x – mate by Black” for now. (Note : Jacobi v0.7.5 should be ready in about a week).

  7. Nicolas Dupontdupont says:

    Crossed messages, Alexandre! Your first one wasn’t visible on my computer when I published mine, whose content is quite similar…

  8. Mario Parrinello says:

    My idea (reverse colors as per Alexandre or inverted colors as per Nicholas) of having White as humanity was suggested in order to have the Pandemic condition more suitable for help stipulations and thanks again for presenting this new fairy condition, Alexandre!
    Glad to hear that the new verion of Jacobi is almost ready!

  9. shankar ram says:

    Well, it had to come – a fairy condition to mark the current state of the world.
    We, in India, toyed around with something which turned out to be anticipated – anti-koeko chess.
    A bit of gallows humour, though…
    Did anybody invent a “flu chess” in 1918?

  10. David Brown says:

    A brilliant parody! Can’t wait until a Vaccine 3) Rule is created, and if immunity is ever viable for White.

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