A smartphone , comprising: a touch display , and a radar system , implemented at least partially in hardware, configured to: provide a radar field ; sense reflections from a human body part of a user in the radar field ; analyze the reflections from the human body part in the radar field ; and provide, based on the analysis of the reflections, radar data; the smartphone further comprising one or more computer processors ; and one or more computer-readable media having instructions stored thereon that, responsive to execution by the one or more computer processors , implement a radar-based application configured to: present an augmented-reality, AR, element through the touch display of the smartphone , the AR element including a touch input control and related to a real object (120-1), an image (120-2) of the real object (120-1) being presented through an image-capture device on the touch display ; and responsive to a determination, based on the radar data, that the human body part in the radar field is moving toward the touch display , maintain the touch input control at a fixed location on the touch display , even if the image of the real object (120-1) is no longer presented on the touch display due to a movement of the smartphone . a touch display , and a radar system , implemented at least partially in hardware, configured to: provide a radar field ; sense reflections from a human body part of a user in the radar field ; analyze the reflections from the human body part in the radar field ; and provide, based on the analysis of the reflections, radar data; the smartphone further comprising one or more computer processors ; and provide a radar field ; sense reflections from a human body part of a user in the radar field ; analyze the reflections from the human body part in the radar field ; and provide, based on the analysis of the reflections, radar data; the smartphone further comprising one or more computer processors ; and one or more computer-readable media having instructions stored thereon that, responsive to execution by the one or more computer processors , implement a radar-based application configured to: present an augmented-reality, AR, element through the touch display of the smartphone , the AR element including a touch input control and related to a real object (120-1), an image (120-2) of the real object (120-1) being presented through an image-capture device on the touch display ; and responsive to a determination, based on the radar data, that the human body part in the radar field is moving toward the touch display , maintain the touch input control at a fixed location on the touch display , even if the image of the real object (120-1) is no longer presented on the touch display due to a movement of the smartphone . present an augmented-reality, AR, element through the touch display of the smartphone , the AR element including a touch input control and related to a real object (120-1), an image (120-2) of the real object (120-1) being presented through an image-capture device on the touch display ; and responsive to a determination, based on the radar data, that the human body part in the radar field is moving toward the touch display , maintain the touch input control at a fixed location on the touch display , even if the image of the real object (120-1) is no longer presented on the touch display due to a movement of the smartphone . <EOS>