1. A method for controlling access to a device, the method comprising: receiving, at the device from a remote device, a plurality of exercises to be presented to a device user and a condition for presenting the plurality of exercises; determining, at the device, whether the condition is satisfied; restricting access to the device in response to the condition being satisfied; presenting, at the device, an initial exercises of the plurality of exercises in response to the condition being satisfied, a difficulty level for an initial exercise of the plurality of exercises based on a pre-determined proficiency of the device user; determining, at the device for each exercise after an initial exercise, a probability of the device user successfully performing a current exercise of the plurality of exercises based on whether the device user correctly performed a previous exercise, a proportion of other users successfully performing the current exercise, and a variation in proficiency of the other users that successfully performed the current exercise; adjusting, at the device, the difficulty level for the current exercise based on the determined probability; and granting, at the device, access to the device upon successful completion of a set of exercises of the plurality of exercises.