Most sleep-sound apps hand you one looping track. Sleep Sounds is a mixer instead: layer royalty-free sounds — brown noise, pink noise, white noise, rain, forest birds, ocean waves — at your own volumes to build the exact environment that gets you to sleep. A gradual-fade timer avoids sudden silence, background playback survives screen-off, and a home screen widget starts your mix in one tap. A streak tracker helps the habit stick. Also useful for focus and meditation, not just sleep.