I am curious if anyone of you know of or use a tool you can play around with layout to use as a reference, currently I would just use paper and pencil to write down ideas for screens, modals, and features, then use a drawing pad on my phone to put down boxes that represent where the content will be placed. It is an arduous task, but it really helps me focus as I suck at being very creative when I code since I just sit there changing colors or sizes for hours till it looks ok to me.