One button, one function. Drag & Drops wherever obvious & telling iconography everywhere is the name of this game. A first-time user's attention span for your app is measured in picoseconds at first impulse, then the timescale extends to a couple microseconds if the product's novel. Finally, if the app's powerful as well as unique to all creation, maybe you've nabbed a few more colossal full-on seconds. Once you catch their flickering eye in a solar flash, keep it sticky with a continuously delivering promise of "Power". Super Power!