The interaction with this toy is more complicated than the other two, but is also much more immersive. The basic interaction would be a user drawing a series of slightly different images on small semi-transparent cards with a thick black marker, and then setting them up in order on the clips below. The clips are mounted on what is basically a turntable, and once the turntable is turned they rotate about a light source mounted at the center(The light source will be more intense and more concentrated than that of a flashlight, but for the purpose of conveying information the flashlight is an identifiable symbol.) At a certain speed, it will work like a flip book and appear to be an animated film loop.
Principles
The reason the sucessive images appear to be a single image in motion is the way our brains process visual information, this toy is essentially a very complicated optical illusion. The principles behind why our brains do this are complex, but that you can trick yourself into seeing one thing as another is a fun lesson. The distance of the light source from card, and card from wall, will effect the clarity and size of the image, and can teach about diffraction and light dispersion. Adding colored filters, or different materials to the clips instead of plain paper can teach a few lessons about how colors 'add' and 'subtract'. Changing the speed of the turntable can provide a lot of fun, tricking the viewer into seeing a static or backwards moving image. There are lots of opportunities to play with some relatively basic physical properties and have actual fun doing it.
Feasability
While this would be an expensive toy, it would not be obscenely expensive. One could modify a slide a viewer or turntable to make one, or you could start from scratch. The motor would have to be relatively powerful, and the fabrication process would be complicated.
I think this would be quite durable. One major advantage is that it does not, as a unit, move anywhere during use. The only moving part is the turntable. This reduces a lot of opportunities for failure. The major issues would be protecting the electric wiring, protecting the light source, and making the clips replaceable (which is preferable to very durable clips because I would rather the clips yield than the user yield in case someones finger gets caught in it.)
I think this toy is quite safe. The only major source of injury would be hair or something like it getting caught in a clip while the machine is spinning. As long as the torque applied is sufficiently low, and the table itself sufficiently light, I do not think this will present a major problem. Other possible sources for injury are the cards and writing implements, but the kit could come with rubber stamps instead of something long and sharp. This also opens up a market for different stamp 'sets' (Animal stamps, Dinosaur stamps, etc.) The stamps would be of arms, legs, torsos, and this way you could still animate. As it stands, I wouldn't recommend the toy for anyone below the 8-10 range without parent supervision, and would recommend parent supervision for 12 and under. If this were sold with the rubber stamps instead, and designed with a kid in mind, I think it could be appropriate for people as young as 6 or 7. Alternatively, if some of following extensions are added and the toy is marketed to a different group, it could be a toy almost exclusively accessible by young adults and older.
Extensions and Improvements
At the most basic, I don't think this toy is incredibly compelling, but there are a few basic improvements that I think would make this into a really great toy. The first is having the light source blink. The two possibilities are scaling the blinking frequency to the frequency of the clips passing in front of it, which would make the movies a little cooler and the ability to understand how frequency and perception react much easier. The other possibility is having the frequency user controllable, with some sort of designations on the knobs indicating which frequency matches which turntable speed. This would have the added bonus of more freedom, which inevitably means more things to learn. The downside is that it could be overwhelming and inconvenient if someone just wants to play with an already time consuming device.
Another extension would be to replace the slides with 3D sculptures. The light source would move to under the sculptures, so that they would be lit on all sides, and the pins would be replaced with something you could mount the sculptures on. My initial thought was to have sculpey or clay come with the set, and let someone go from there, but you could just as easily mount legos onto the edges and they would be just as (if not more) fun. The biggest issue would be accounting for centripetal force, and making sure the sculptures don't deform (more a problem for clay than legoes), but I think the 3D flipbook would be a really exciting toy.
