JamCatWow is a collection of free daily puzzle games. Each game has one puzzle a day, the same for everyone, in any browser: nothing to install and no accounts, so a class can play the day's puzzle together on one screen, or each student on their own.
Students build words from the day's letters in 5 minutes. Longer words score more, and one word uses every letter.
Students add, subtract, multiply and divide six numbers to reach three targets in 3 minutes, whole numbers only.
Students see a color, then rebuild it with hue, vividness and lightness sliders, and are scored on how close they land. Three rounds, no clock.
Students place five real quantities, how heavy, how far, how long ago, on one scale where each step is ten times the last, then say how sure they are.
Students plan a route across a pond that steps on every tile exactly once, around stones and across ice that slides.
On one screen. Put the day's puzzle on the projector and play it as a room: the class calls out words in Anagrams, argues the arithmetic in Numbers, votes on the color in Colors, debates the estimates in Ballpark and plans the route in Thin Ice. Nothing to hand out, no devices, no accounts. The site opens in its dark theme. For a projector, the moon button in the header switches it to light. Anagrams and Numbers run on their own clock. Colors, Ballpark and Thin Ice wait for the discussion.
On their own devices. Each student opens the same puzzle and plays it alone, and the timed games finish everyone together. Comparing is by hand: what a student shares is a score card that shows how they did and never the answer, so scores can be compared before the last player finishes. There is no class code and no teacher view, and on a shared computer two students' results and streaks will mix.
What a student shares, for Anagrams: the score, the tier and how many words were found. Never which words.
Two things to plan around. The puzzle is the same all day, so a class that plays in the afternoon can hear the answer from one that played in the morning. And there is no preview of tomorrow: to vet a puzzle first, play today's yourself before class, or use a day from the archive you have already seen.
Either way, rules first: every game has a short how-to page, linked above, that a class can read together. Missed a day? The last two weeks stay playable in the archive, free.