Samsung is delving into the complexities of bringing its mobile payment platform to the Gear S3 smartwatch.

There were a couple of major obstacles to overcome. For one thing, it was difficult to fit into the small body of a smartwatch both the NFC antenna and the antenna for MST, the technology that allows Samsung Pay to emulate traditional stripe cards for use with older POS terminals. The battery also had to be refined to consistently power the app, and eventually all the components had to be arranged in such a way as to make the payment process intuitive with any standard POS terminal, a design process that entailed “countless hours collecting data at various shops,” according to a statement from the company.

The challenges may help to explain why the mPayment service took so long to make it to a Samsung smartwatch. After a long delay, it finally arrived on the Gear S2 smartwatch this past summer, but without MST technology to support it, and with a setup process that some found clumsy.

Now, Samsung is clearly hoping the mPayment option will help to drive the popularity of the Gear S3, and vice versa, and to that end is once again stressing the service’s ease of use. As Samsung Electronics Payment Biz Group Senior Manager Shankar Narayan illustrates with his own anecdote, when he went to pay for a soft drink using his Gear S3 at LAX, “the receipt was already printing” by the time a stunned cashier could ask what he was doing.