Boop is played on a 6×6 bed. You each start with eight kittens in
hand, and you win by getting three of your cats in a row. Orange places
first.
A turn
Place one piece from your hand on any empty square. That is the whole
turn: pieces already on the bed are never picked up and moved, they only
ever get pushed around by what you place.
Booping
The piece you place pushes — boops — every piece in
the eight squares around it one square directly away from itself. Yours
and your opponent's alike.
- A piece only moves if the square it would land on is empty. If
anything is already there, it stays where it is.
- A piece booped off the edge of the bed goes back to its owner's
hand.
- Kittens cannot boop cats. A kitten you place shoves
the kittens around it and leaves the cats standing. A cat boops
everything.
Every direction is worked out from the square you played, so a piece can
be booped at most once per turn, and no boop can open a gap for another.
Graduating
Once the booping has settled, look for three of your pieces in a
row — along a rank, a file or a diagonal, on adjacent squares. All
three come off the bed and go back into your hand as
cats, whether they were kittens, cats or a mix of the two.
It does not matter how the line came about: the piece you placed need not
be in it, and a row you shunt your own pieces into by booping counts just
the same. Only the player who has just placed can graduate, and if there
is a line, graduating is compulsory. Make two lines at once and you choose
which one goes.
Winning
- Three of your cats in a row wins on the spot. The
line is not graduated — the game is simply over.
- Getting all eight of your pieces onto the bed as cats
also wins.
When your hand is empty
If all eight of your pieces are on the bed you have nothing left to place,
so your turn is a different thing: take one of your own pieces off the
bed, graduate it, and put it straight back down as a cat on any empty
square — including the one it has just left. It boops from there
like any other placement, and can complete a line like any other.
Where this board differs from the printed rules
Two known gaps, shared with the engine this board takes its rules from:
- A line you shove your opponent's pieces into is not spotted.
Only the mover's own pieces are ever checked.
- The empty-hand turn here lets you graduate a cat as well as a kitten;
the printed rules allow only a kitten.
This is an analysis board, not an opponent. Nothing here plays against
you: you play both sides, branch wherever you like, and step back and
forth through what you have built.
Playing a move
- Click an empty square to place a piece there.
- If you hold both a kitten and a cat, a small picker appears in the
colour of the side to move. Otherwise the only piece you have goes
straight down.
- A placement that completes one line graduates it for you. One that
completes two stops and lists them; hover an option to see that
line lit up on the board, and click to take it.
The empty-hand turn
When every one of your pieces is on the bed, the board asks in the order
the move happens:
- Your pieces are ringed. Click the one to graduate — it takes a
heavier ring.
- Every square the cat may go to is dotted, the square it came from
included. Click one to play the move.
Clicking a different piece of yours picks that one instead, and
Esc clears the selection.
Moving through the line
Click any move in the list to jump to it, use the left and right arrow
keys, or scroll the wheel over the board — up steps
back, down steps forward. The move you are on is highlighted, and the list
keeps it in view.
Variations
Play a move that differs from the one already recorded and the line
branches. Right-click a move — or use the buttons under the board
— for:
- Promote variation — move that line up one level
among its siblings.
- Make main line — make it the principal line,
demoting the rest by one and keeping their order.
- Delete from here — remove the line from that
move onward.
All three act on the point where the line diverges rather than on the move
you happen to be looking at, so promoting from deep inside a variation
does what you mean.
Position
The FEN box holds the position you are looking at. Copy
it out, or paste one in and press Load FEN to start a
fresh line from it.
Move list
The Move list box holds the line as text. It shows the
main line — whichever move comes first at each branch, which is what
make main line decides. Tick include variations
to add the branches in brackets, PGN-style:
1. Kc3 Kd4 2. Kc4 (2. Kb1 Kf6) (2. Ke5)
Load moves reads that back, variations and all, so
exported text pastes straight in and every branch stays clickable. A
bracketed group is an alternative to the move just played, so it branches
from the position before it.
Notation
Squares are named like a chessboard: files a–f
left to right, ranks 1–6 bottom to
top, so a1 is the bottom-left corner.
Kc3 | place a kitten on c3 |
Cc3 | place a cat on c3 |
a1>Ce3 | hand empty: a1 graduates and is placed, as a cat, on e3 |
Kc1=a1b1c1 | the placement completed that line, and it graduates |
a1>Ce3=c1d2e3 | both at once |
Kc1=a1b1c1# | and it won the game |
= echoes chess promotion, which is what graduation is.
> reads as "becomes", written source-first because the
piece leaves a1 before the cat lands on e3. Every token says
exactly what happened, so a game replays from its move list alone.
The board editor
Board editor at the foot of the page sets up any
position. Five tiles appear beside the board — a kitten and a cat
for each side, and a cross that removes pieces. Click a tile to pick it
up, then click squares to place that piece over and over.
Choose whose turn it is and how many kittens and cats each player holds.
Every player owns exactly eight pieces counting the bed
and the hand together, so a total that does not add up keeps
Continue from here disabled until you fix it. Continuing
leaves the editor and starts a fresh line from that position.
A line that starts anywhere but the opening position carries a tag at the
top of the move list saying where, and the tag is written into the
exported text and read back on import:
[FEN "6/4B1/3a2/2a3/6/6-60-70-bp"] 1... Ka1 2. Kf6
Either side can move first from such a position. When grey begins, the
first move is numbered 1... rather than 1., as a
chess game continued from black's turn would be.
Menus
| Board | theme and a lightness slider |
| Pieces | theme, a colour picker for each player, a lightness slider, and a reset |
| ⚙ | coordinates, how variations are laid out, whether square highlighting sits behind or in front of the pieces, and the booping animation and its speed |
All of it is remembered between visits, in your browser. Drag the
bottom-right corner of the board to resize it.
What is not kept
The line you are building lives in this tab and nowhere else, so a reload
clears it. Copy the move list out if you want to keep it.