1. One or more computer-readable media storing computer-executable instructions that, when executed, cause one or more processors to perform acts comprising: providing a first user input mode that restricts display of an input into a text field to a first set of characters; at least partly in response to receiving an input from a user specifying a character of the first set of characters, causing display of a character within the text field in a first manner; at least partly in response to receiving an input from the user specifying a character that the first set of characters does not include, refraining from causing display of a character within the text field; providing a second user input mode that restricts display of an input into the text field to a second set of characters that differs from the first set of characters; at least partly in response to receiving an input from the user specifying a character of the second set of characters, causing display of a character within the text field in a second manner that differs from the first manner; and at least partly in response to receiving an input from the user specifying a character that the second set of characters does not include, refraining from causing display of a character within the text field.