The 2 halt-trot transitions involve "parking" the pony in front of an obstacle, the handler passing through and then asking the pony to join the handler at trot. At the lower levels, we had to learn to park the pony in front of an obstacle and then join the handler at a walk. So we have the elements of "halt", "wait" and "join me" already in place and Fat Pony is really quite good at that now. The challenge is now to teach Fat Pony "join me at trot" and to have him be able to understand the difference between "join me at walk" and "join me at trot", since either might now be required in a competition and I don't want Fat Pony to start anticipating one or the other. The parallels with schooling and dressage training are clear!
The trot-halt transition is even more interesting, as the obstacle is to trot the front feet only over the pole and then halt. So not only does the transition have to be super accurate, but the pony has to be quite confident about halting with the pole under the middle of his tummy, where he can't see it very well! To trot over the pole without touching the pole will require an active trot going into the halt - the beginnings of collection and taking the pony's weight back onto his hindquarters!
The more involved I get with Horse Agility, the more I see the benefits and the challenges. It started out as something fun to do - and it still is fun, more than ever! - but it's also taking us on a journey that is about developing and refining communication; and about developing the pony's suppleness and fitness; as well as keeping his brain busy and having fun :-)