Basically, it's a page that shows one or more random words or images from a chosen set and changes them every time you click a button. Think of the three windows of a slot machine. I use it for the parts of speech and other directions in a make-a-sentence game, but you could do anything with it. To see what I mean, take a look at a couple of sample pages. One uses text for each element (note that each can be different color; you could also frame the elements, again in different colors, to visually separate them more). The other uses images--that lets you illustrate each element and add yomigana if you like to make it easier for elementary kids who would have trouble reading.
So far I've been doing this with physical sentence cards. I usually have the kids pair up, pull up a set of cards, discuss how to say it in English (add third-person "s" or not, or whatever fits the day's instructions; or I might start with a set where none of the subjects require the "s") and the meaning in Japanese, then go up to either me or the other teacher and show us their tablet, then one says it in English and the other in Japanese (switching off every time, of course), then they go back to their desks and write it on a worksheet. Then they push the "Change" or "New Sentence" button to get new cards and do it again. I usually start off with three cards--subject, verb, and object--and first have them make positive sentences, then negative, then interrogative. Then I'll switch them to a four-card set where the fourth card is either 〇, ✖, or ❓ and they make the appropriate positive, negative, or interrogative card. The meanings of the cards often don't mesh up well, which leads to crazy sentences which entertain and hold the kids' attention and (I think, at least) focuses their thinking on the sentence structure.
Depending on the point of the class, I might have them use past, present, or future tense, or use "have to," don't have to," etc. I don't even have to make a new set for each way I use it--I just change what I tell them to do with one of the basic sets above. It's something I can always pull out of my hat at the last minute or if I don't have time to prepare anything else. I've got a cut-up-paper game where kids take random strips, each with a whole clause, then choose a relative pronoun and put them together--it'd be super easy to turn that into a page like this. Heck, I could get fancy and add a box for kids to type a sentence into right on the page, under the cards, then have them send me screenshots in Loilo--I might even be able to make a whole online worksheet, where each kid gets their own unique set of ten sentences to make, then sends it to me (I'm not sure if there's a limit to how many random elements I could put on a page--more than five or six might take some figuring out). Math problems would be super easy--you could even vary the operator sign randomly.
Now that I can make a new version just by dumping a list of words into a copy of one of these pages, making a few very simple changes, and uploading it to our site, I can make new versions very quickly. No printing, cutting, and laminating. And once done, I don't have anything to keep store, carry around, lose, or wear out.
If you want to make your own version and you're not up on hand-editing html, you can just send me a list of words or a folder full of images you want to use, tell me the order you want them on the page, text colors, anything else you want the page to say, etc. You could also tell me you want to use one of the existing versions but with some words or cards added or taken out. Give me a day or two in case I don't have time right away, but it'll actually take me less than an hour to adapt it and get it up on the site--a lot less if you just want text cards with no images.
If you do want to use image cards, you can help me out by sizing them appropriately. The important bit is width. You want the total width of the cards to be less than about 1300 pixels (the student tablet screens are 1368 pixels wide, minus a bit for edges and boring technical reasons, and a bit more if you want borders around each card). So if you want to show three cards side-by-side, make each less than 433 pixels wide (you can make one set wider and the others narrower, too--it's the total that counts); if you want four cards, 325 pix wide each. And make heights reasonably proportional (no more than 550 pix; if you want two rows of cards, no more than 275). Format should be jpg or png.