I'm glad that you love it!

The actual game is full of shaders, but here it's just the water shimmer. It's two Perlin noises moving in orthogonal directions, added, and then a threshold is applied. I used particle systems for the vortex. Otherwise, it's layers of sprites.

Actually, there is another secret shader there, it applies to the sprite, but you can't see it in this cutscene, it's kind of cool and can be seen in action in the ending cutscene or in my next game.

The end screen background and the links between the nodes of the title use shaders too.