Simple, advert free, works

No adverts or settings or anything else cluttering the screen at all but the colours themselves. Controls are easy to change: movement(tap), colour(tap&hold) or blob-size(pinch). Altering the size changes the colour intensity and brightness the larger the blobs are. Nice slow movement. Fills a dark room with relaxing colour exactly as you'd want an old school lava lamp to. Only criticism is there's a little too much white on some colours getting in the way of the colour and the effect would better if it was pure colour with no white light but some colours have no white in the screen at all and others have white and colour mixed together so you can choose what you want easily.