Decker includes a variety of transition effects which can be played when a user moves between cards. The built-in effects generally composite the source and destination card together somehow, but it's possible to write custom transition functions which do pretty much anything as long as they execute reasonably quickly.
This idea has lived rent-free in my head for several months, and ultimately I was forced to implement it. Perhaps now it will live in some of your decks as well...
With a few small tweaks to the utena module, it is possible to ask Decker to record perfect loops and thus Grasp Eternity.
The commented lines show changes or additions:
Note that Decker makes no effort to compress GIFs it generates; it's a good idea to run the output through an optimizer like gifsicle before sharing them.
