I need to seamlessly implement micro-payment option within my web app.
Some use cases/requirements include:
user has 3 purchase options (and receives a number of coins per options) which should be handled via paypal-micropayments
user can "gift" a number of coins to another user
deduct coins once used or gifted
apply offer code for discount
keep track of user payments for pro-rating tier movement (i.e. if middle option = $10 and low = $2; then i want to charge user only $8 to move from low to middle (so must keep track)) etc.