I was presented with this situation recently in Letter Jam, a co-operative word deduction game from newcomer Ondra Skoupý and publisher Czech Games Edition. I played Letter Jam twice in near-final prototype form at Origins Game Fair 2019, was offered a mock-up copy from that fair for further playing, played twice more on Sunday night after packing up the BGG booth and having dinner, then played twice more since I returned home.
Like Codenames, the 2015 deduction game that propelled CGE into the party game market, Letter Jam inspires cleverness in both the clue giver and the clue receiver. You're presented with an unusual situation — a situation similar to what you'll see in other playings of this game, but a situation unique to these particular circumstances — and you must create a clue that takes advantage of that situation as best as possible.
Each player in Letter Jam is trying to guess the letters spread face down before them in order to guess the word they were given at the start of the game. Only one letter a time is visible from each word, and these letters are visible to everyone other than the person who "owns" the letter.
In more detail, at the start of play, each player places their leftmost letter in a stand facing everyone else, with dummy letters added to the table so that six letters are visible no matter the number of players. An asterisk representing the joker is placed in the middle of the table. All players think of clues that use letters owned by other players, letters owned by dummy players, and the joker, then they say how long their clue word is, how many players' letters are used (but not which players and how often those letters are used), how many dummy players' letters are used, and whether the joker is used. Anyone can throw out clue parameters, then players debate whose clue they should use.
So what ten-letter clue did I give in the picture below that used all the available letters and the joker?
"Millimeter."
Note that you don't say your clue word. Instead, you spell out the word letter by letter by placing numbered tokens next to the letter or joker being used. This means I placed the 1 by "M", the 2 by "I", the 3 and 4 by the joker, and so on. (The mock-up game that I have includes only tokens numbered 1-8, so I just pointed at the letters while saying "Nine" and "Ten".)
Each player whose letter was used — all of them in this four-player game — writes down all that they know from what they see, so the player with an "M" would write _I**I_ETER on their personal note sheet, while the player with the "R" would write MI**IMETE_. Ideally you can give a clue that allows each other player to determine with certainty what their letter is. If they do, they put their letter face down on the table — without looking at it! — then place the next letter in their letter row in their stand; if they aren't confident about what the letter is, they might write a few guesses next to the clue word so that they can better narrow down their choices with the next clue they receive.
By the final round of the game, ideally you know all your letters and can anagram them into a word. (If you guess your letters before game's end, you have a chance of earning bonus letters.) You don't necessarily have to create the same word that you were given; if you receive the letters ABDER, for example, you can spell three different words, and any one of them counts for the victory condition. If you goof up on something, as with my notes below in which I recorded GASN, then realized that I couldn't possibly create a word with the fifth letter, you can claim the joker or a bonus letter from the center of the table and overlay one of your letters so that you can form a word.
Letter Jam is a phenomenally smart design. As with Codenames and to some degree Decrypto, you need to give clues to your fellow players that work on multiple layers. Longer words tend to be better for clues because they'll give players more to work with, but sometimes you just can't make it happen! If you're staring at five consonants like F, M, C, G, and W, you could use the joker to clue two people in with the word MIMIC, but you might be better off hoping that someone else can step with a clue of their own.
The more often you give clues, though, the less you learn about your own letters, so you need everyone to participate. You want to use as many player letters as possible, but of equal importance is giving them a clue distinctive enough that people can make a leap, then move on to their next letter. (In a six-player game, I gave a clue of LACTATE that let all five of my teammates guess their letter, and I felt like cheering.) This keeps everyone moving toward victory, but it also just gives players a different assortment of letters each round. In my six games, the worst experience has been getting a couple of short clues that told no one anything and left us staring at the same letters as before.
You're also incentivized to use the dummy player letters, should have fewer than six players, because if you use all of the letters stacked before a dummy, you receive an additional clue token that gives all players one more round in which to deduce what they have.
To make one more comparison with Codenames, Letter Jam is highly group dependent. I played a game with my ten-year-old son, for example, so the three adults at the table had to pitch their clues toward his age range. During a demo game at Origins, I realized after giving a clue of SUFFERS that I could have given the more detailed clue (sans joker for the R) of SUFFUSES, but a couple of players were having trouble figuring things out — not deducing their letter from the clue of _CON_C, for example — so a clue of SUFFUSES probably would have been as useless as my clue of SUFFERS. So much suffering in that game...
In another demo game at Origins, I hit upon the perfect clue for my four teammates, but I could not possibly give that clue as it was a word I would have used only among people I know extremely well. So be it. Better to lose the game than create a bad reputation for you and your employer — and in the end we all deduced our words anyway.
While Letter Jam shares many traits with Codenames, it's not comparable in ease of play. Each player has to know what they're doing, and if someone can't figure out a letter or two, then all you can do is throw more clues at them or try to race through your own letters so that you can pile bonus letters onto the table that they can use at game's end. If a player can't come up with a clue longer than four letters, at some point you shrug and say go ahead because you need everyone to give a clue in order to unlock a bonus clue round — and maybe that four-letter word will help more than you think. AMOK would be a wonderful clue, for example, as long as it doesn't include a joker because everyone should be able to figure out their letter from seeing _MOK, A_OK, AM_K, or AMO_, right? That's the hope anyway...