Bench and table-bench combinations, complete with shade umbrellas, are mounted on moving platforms, each with their own orbit: smaller ones around larger ones, all circling (or ellipsing as the case may be) an open water feature play area. The benches and tables are perfect for sunning, chatting or
playing checkers; the pool in the middle is suitable for children, ages 8 and upwards.
The object of the game for the pensioners is to try and rope the kids into listening to rambling, pointless anecdotes; failing that, each bench is equipped with holstered wiffle-bats to send them on their way.
The object of the game for the kids is simpler: try to get to and from the pool by weaving amidst the moving platforms without being trapped or swatted.
[addendum]
Game aside, this provides a generic "safe zone" for both parties: the youngsters are old enough to play without personal supervision, but the presence of the oldsters will help to shoo off the guy wearing an overcoat on a warm, sunny day; likewise any bullying has reliable witnesses.
On the more sedate side of things, a purse-snatcher is going to have to spend a bit of extra time calculating an approach vector so is more easily spottable. Even if a mugger is desperate enough to ply his/her trade while standing on a moving platform, there's still the problem of threading an everchanging maze to escape. An agile youngster might even be able to get back with help before the robber emerges.
While platforms *can* be boarded while in motion fairly easily, they extend to the outer limit of their orbit and park themselves when weight is removed from the seats, then resume the "celestial dance" when people sit down on them.
[originally titled "Ornerorrery"]