Perennial is a platforming game.
There's lot's of running and jumping and collecting coins with a bit of a combo mechanic to keep up the pace.
The levels are fairly linear with a bit of interwoven backtracking, usually on some new path through the level - an opportunity to find a secret area perhaps.
The intention here is to have smooth technical operation combined with a pure aesthetic that isn't gummed up by standard things like words. The story, such as it is, is revealed silently. This may mean some people won't know what's going on.