Ah yes, yet another service that wants my email address without ever telling me what for, no privacy policy, no promise not to spam, nothing but vague but unhelpful description of a service.
Is hiding an input element really more functional than just having an input field appear on the page? The simple fact that it required instruction to use: "Hint: click or drag on the page" (and rather ambiguous instruction too as there are 2 "pages") belies the functional simplification that it seems to present.