TiddlywinksETwA rules · singles

The rules, and where each number comes from

This game follows The Official Rules of Tiddlywinks (2016 version) as approved by the English Tiddlywinks Association and sanctioned by NATwA and IFTwA. Rule numbers below are ETwA's. The rules text is © ETwA and is not reproduced here; only the factual constants are used, and each is cited.

Equipment

Squopping

A wink that comes to rest vertically above all or part of another unpotted wink squops it (rule 8.2), and it does so even if the two are not touching (rule 8.2.1). A squopped wink may not be played (rule 10.1); the wink on top may. Two or more winks connected directly or indirectly by that relation form a pile (rule 8.2.2), and one wink can be squopping and squopped at the same time (rule 8.2.3).

Potting and the turn

Colours play in alphabetical order — blue, green, red, yellow (rule 7) — with blue partnering red and green partnering yellow (rule 1.1). Potting a wink of the colour being played earns an extra shot, one per wink potted (rules 12, 12.2); potting somebody else's earns nobody anything (rule 12.3). Sending one of your own winks off the mat forfeits your next shot with that colour (rule 14), and the wink is brought back on from the boundary (rule 13.1).

Scoring

The four colours are then ranked and awarded game points, ties sharing the aggregate equally, and partners' points are added (rule 19.2) — so a pairs game always totals 7. If a colour pots out, the game runs on until a whole partnership is out, colours score by the order they potted out, and one point transfers from the losers to the winners (rule 20.2).

Ending

Three ways (rule 16): the timed period — — followed by further rounds after the squidge-off winner's turn (rules 17, 18); a partnership potting out (rule 20); or no wink being playable at all because every unpotted wink is squopped (rule 21).

Squop-up turns

If a partnership ends a turn with no free winks it is squopped up, and the opponents get one more turn than there are winks on the field of play that are not part of a pile (rule 22.2). Before those turns run out they must play a freeing shot (rule 22.4); failing to leaves the next colour with a free shot using a nominated colour (rule 22.6.1).

Shots on a pile

A shot on a pile does not only move the wink on top. Rule 10.3 lets the squidger touch winks that were vertically below the first wink played, and Note E.4 says a shot may deliberately attempt to move a squopped wink a large distance without necessarily moving the first wink played a significant distance. That is the boondock. The Dig under control is how much of the squidge goes to the wink underneath: none of it and you play the top wink off the pile; most of it and the top wink barely stirs while the wink beneath is sent across the mat.

Named shots this game recognises

How the squidge is modelled

Pressing a squidger down on a wink and drawing it off the edge does not flick the wink the way a finger flicks a coin. Cambridge University Tiddlywinks Club describe the mechanism plainly: the wink is pinched between the squidger and the felt, the felt compresses, and when the squidger slides off the edge the mat returns to its original shape, pushing the wink away. The spring is the mat. The squidger's own flex is a separate, specialised trick — the “phone card” shot for a wink sitting right against the pot.

One impulse, two results

The engine models the release as a single impulse applied a small distance from the wink's centre. That one geometric choice makes the launch speed and the spin come out coupled:

ω / v = ℓ / k², with k² = I₁/m = r²/4 + h²/12

So a player never sets spin on its own. Tilting the squidger towards the target (squop-style) puts the line of action near the wink's centre and the wink stays level in flight; tilting it away (pot-style) moves it out and the wink flips over. Reconstructing three shots that Rick Tucker photographed at MIT in 1979 puts that offset at — and pot-style is the squop-style figure.

Why distance, not force, decides how the wink lands

With the spin ratio c and the launch elevation α both fixed by how the squidger is held, the total rotation in flight works out as

φ = c · x / cos α

which does not contain the launch speed at all. Hit the wink harder and it goes further, but it arrives at that further place with exactly the attitude it would have had there anyway. The only way to change how the wink lands at a given distance is to change the squidger. That is why the Squidger tilt and Squidger angle sliders matter as much as Force.

Where the numbers come from

DOCUMENTED stated by a source, of this exact thing. qualified documented, but of something adjacent. MEASURED read off a published measurement of a real shot. DERIVED computed from those by stated algebra. CALIBRATED fitted so the engine reproduces a measured shot. RECONSTRUCTED no source; invented here and declared as such.

What is honestly reconstructed

The felt's stiffness and energy return, the mat's friction and restitution, wink-on-wink friction, the pot's wall thickness and the exact shape of its concave curve, and every decision the opponent makes. No source gives any of those. The existence of the mat spring is documented; its numbers are not.

About this game

Tiddlywinks is a public-domain parlour game. The bank clerk Joseph Assheton Fincher (1863–1900) filed the original patent in 1888 and applied for the trademark Tiddledy-Winks in 1889; John Jaques & Son were the exclusive distributors of the game under that name. The modern competitive game was devised by undergraduates of the Cambridge University Tiddlywinks Club from 16 January 1955, and its rules have been maintained since 1958 by the English Tiddlywinks Association, with the North American Tiddlywinks Association (1966) and the International Federation of Tiddlywinks Associations (1963) alongside it.

This is an independent reimplementation. It is not published by, endorsed by or affiliated with ETwA, NATwA, IFTwA, CUTwC or John Jaques & Son. No code, artwork or rules text from anyone else is included; the rules text is © ETwA and is not reproduced, only cited.

What differs from the real game

• A singles game only: you play blue and red, the computer plays green and yellow. Pairs, threes and team play are not implemented.
• The clock advances a fixed amount per shot rather than in real time, so a game finishes in a few minutes instead of twenty.
• Foul shots cannot be played: the interface only offers legal shots, so rules 23 and 24 are enforced by construction rather than adjudicated.
• Winks at rest are laid flat. The real game has winks propped at angles against the pot and on sloping piles; rule 25.4 exists precisely because they do.
• Squidgers are one size. A real player carries up to twenty and picks one per shot.
• The Bristol, gromp, chip-out and pile-flip are recognised and named when they happen, but the interface does not let you set one up deliberately.
• Rule 21 (all unpotted winks squopped) cannot be reached here: with winks strictly stacked, the top wink of any pile is always free. In the real game winks lean.

Sources

• The Official Rules of Tiddlywinks, 2016 version, English Tiddlywinks Association — etwa.org
• ETwA equipment page — etwa.org
• Richard W. Tucker, Tiddlywinks Photography, MIT 6.163 Strobe Project Laboratory term project, 13 December 1979, reproduced by NATwA — tiddlywinks.org
• NATwA, Lexicon of Tiddlywinks — tiddlywinks.org
• Cambridge University Tiddlywinks Club, Tiddlywinks shots — cutwc.org
• Wikipedia, Tiddlywinks

Yan Wang's 2008 MIT report Determining Angular Velocity of Winks Using High Speed Video, linked from NATwA, returns HTTP 404 from every route. It would have given angular velocities directly. No number here is attributed to it.