Such a bizarre interface. It is slow to add items and quantities you want, especially if it not part of predefined set. For the predefined items, one is unable to change the quantities and modifiers to meet their needs. For instance, 'Milk' has quantities of 1, 5 and 2l. I don't buy milk by the liter and frequently I just want to buy 2. It is too easy to mark an item as purchased accidentally. Overall the interface is not intuitive and wasteful of screen space. Beauty over functionality.