A mobile interface to ideate grids and comps. Lego like for simplicity restricts users focus on buliding and nothing more. Scratch that, tetris like is more apt. Quick sync or dump to a desktops or workstation for development. Portable and on the go. Who's interested?
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Drawbacks: your grids might be biased towards the aspect ratio of the screen. Workaround: an app on mobiles if multiple sizes and tablets or foldables could present opportunity to shift mediums and foster creativity by saturation.