A method comprising: at a device with a display: displaying a user interface on the display; determining a first set of content-display values for one or more content-display properties of first content that corresponds to a respective region of the display, characterised in that the method further comprises: determining a first set of control-appearance values for one or more control-appearance parameters based on the first set of content-display values; and displaying a control in the respective region of the display, wherein an appearance of the control is determined based on: the first content; and the first set of control-appearance values, wherein the method further comprises: while displaying the control in the respective region of the display: detecting a change in content that corresponds to the respective region of the display from the first content to second content, different from the first content; determining a second set of content-display values, different from the first set of content-display values, for the one or more content-display properties of the second content; determining a second set of control-appearance values for one or more control-appearance parameters based on the second set of content-display values, wherein the second set of control-appearance values is different from the first set of control-appearance values; and in response to detecting the change in the content, changing the appearance of the control in accordance with: the second content; and the second set of control-appearance values. displaying a user interface on the display; determining a first set of content-display values for one or more content-display properties of first content that corresponds to a respective region of the display, characterised in that the method further comprises: determining a first set of control-appearance values for one or more control-appearance parameters based on the first set of content-display values; and displaying a control in the respective region of the display, wherein an appearance of the control is determined based on: the first content; and the first set of control-appearance values, wherein the method further comprises: while displaying the control in the respective region of the display: detecting a change in content that corresponds to the respective region of the display from the first content to second content, different from the first content; determining a second set of content-display values, different from the first set of content-display values, for the one or more content-display properties of the second content; determining a second set of control-appearance values for one or more control-appearance parameters based on the second set of content-display values, wherein the second set of control-appearance values is different from the first set of control-appearance values; and in response to detecting the change in the content, changing the appearance of the control in accordance with: the second content; and the second set of control-appearance values. determining a first set of control-appearance values for one or more control-appearance parameters based on the first set of content-display values; and displaying a control in the respective region of the display, wherein an appearance of the control is determined based on: the first content; and the first set of control-appearance values, wherein the method further comprises: the first content; and the first set of control-appearance values, wherein the method further comprises: while displaying the control in the respective region of the display: detecting a change in content that corresponds to the respective region of the display from the first content to second content, different from the first content; determining a second set of content-display values, different from the first set of content-display values, for the one or more content-display properties of the second content; determining a second set of control-appearance values for one or more control-appearance parameters based on the second set of content-display values, wherein the second set of control-appearance values is different from the first set of control-appearance values; and in response to detecting the change in the content, changing the appearance of the control in accordance with: the second content; and the second set of control-appearance values. detecting a change in content that corresponds to the respective region of the display from the first content to second content, different from the first content; determining a second set of content-display values, different from the first set of content-display values, for the one or more content-display properties of the second content; determining a second set of control-appearance values for one or more control-appearance parameters based on the second set of content-display values, wherein the second set of control-appearance values is different from the first set of control-appearance values; and in response to detecting the change in the content, changing the appearance of the control in accordance with: the second content; and the second set of control-appearance values. the second content; and the second set of control-appearance values.