This is probably the game with the most minimalist controls I've played all year. You get one stick control (left and right only) and a single button.
You play two children, taking a wander down memory lane. Push the stick forward and time moves in the normal manner. They walk forward, things at height fall to the ground, and causality behaves as you expect it might. Walk backwards however, and the universe gets thrown into reverse. Time goes backwards, things fall upwards, and entropy magically reverses itself.
But since only moving forwards or backwards isn't the most thrilling mechanic, this is actually a puzzle game. Hitting switches will change what goes on around you, and if you interact with the right thing (say a videogame controller or a remote), you can alter a second time stream.
Getting these various different causality threads to line up in a way that allows you to progress is the main aim of your journey through each level. You need to both acquire and transport a bit of light from the start to the end, in order to power the magic space lift that will let you end the level. Separate mechanisms will allow you to hand off that light to robots that will take alternate routes to you, which means that when you walk past a black hole, you don't lose it.
This results in no small amount of travelling backwards and forwards, and can on occasion get a bit frustrating. The levels are circular, which is both aesthetically pleasing and thematically appropriate, but also means sometimes you're trying to follow the path of something you just can't see. A bit annoying. Still, they tend to be impressively built and always contain interesting elements to play with.
This is definitely one of those games that leans heavily on the nostalgia feeling. You'll encounter a lot of things you recognise (assuming child of 80s/90s like me) which does ping that "I get that reference" feeling, but it only partly hides the fairly repetitive gameplay. The various elements you fast forward and rewind are quite cool to look at, but the puzzles they're involved with don't ever feel like they progress. There's simply one more loop added, to something that I would say you could brute force, but really you're solving just by seeing how it works. Not really very satisfying.
Pleasing to look at, and an unusual mechanic, but not actually a very fun game.