Usability of Back of Device Virtual Buttons Tony Morelli Ethan Coggins Molly Rossman Central Michigan U Central Michigan U Central Michigan U Mt Pleasant, MI Mt Pleasant, MI Mt Pleasant, MI [email protected] [email protected] [email protected] ABSTRACT Back of device touch screen capable game systems have been commercially available since the release of the Playstation Vita in 2012, however the use of these touch screens in games has been limited. With the release of the touch screen lack- ing Playstation Vita TV, it seemed as though the use of the second touch screen would become even less common as developers produce games with features common to both platforms. Back of device touch was revived with the release of the Playstation 4 with the purpose of mapping DualShock 4 inputs unavailable on the Vita to sections on the back of the device during remote play. This paper seeks to under- stand the limitations of using back of device touch screens for game input. Four selection tasks involving a total of 30 participants compared the reaction times and accuracy for 13 different back of device touch region layouts. The re- sults found that the usability of the back touch screen on a Figure 1: Playstation Vita and its Back of Device Playstation Vita was in line with standard game controllers Touch Screen and the performance significantly decreased when 12 or more virtual buttons were present. Playstation Vita games offered different control options which Categories and Subject Descriptors typically included options to either use or not use the touch H.5.m [ Human Centered Computing ]: Graphics Input screen on the back of the device. Although all games re- Devices; Pointing Devices; Touch Screens leased for the hardware platform could take advantage of the second touch screen, very few relied on it as the only Keywords control mechanism. Playstation;Vita;Fitts;Back;Touch;Interactions;Usability Sony announced the release of the Playstation Vita TV [14] in 2013. This device would be compatible with games re- 1. INTRODUCTION leased for Vita, however it displays on a TV and uses a When the Playstation Vita (Figure 1) was released in early DualShock 3 as a controller. Developers wishing to release a 2012, it offered unique input control mechanisms. In addi- game to the highest population of consumers would release a tion to containing standard mobile input mechanisms such game that functioned properly on both a Vita and on a Vita as a touch screen, microphone, and accelerometers, it also TV. This could mean future games would not contain con- included standard dedicated mobile gaming device controls trol features specific to the Playstation Vita as it would be such as thumbsticks and dpads. The combination of these difficult to maintain both methods of control. Developing a two standard device controls was enhanced by also offering game that required Vita second screen touch would alienate a touch screen on the back of the device. the population who only owned a Vita TV from potential purchasers. The release of the Playstation 4 found a new use for the back Permission to make digital or hard copies of all or part of this work for of device touch screen on the Playstation Vita. Playstation 4 personal or classroom use is granted without fee provided that copies are features Remote Play [13], the ability to mirror the contents not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. of the Playstation 4’s display on the Vita display. In addition Proceedings of the 10th International Conference on the Foundations of to mirroring the video feed, Remote Play also allows players Digital Games (FDG 2015), June 22-25, 2015, Pacific Grove, CA, USA. to use the Vita as a controller. This feature makes it possible ISBN 978-0-9913982-4-9. Copyright held by author(s). for a gamer to play Playstation 4 games in the living room using the Vita, while the main TV is used for viewing other content. The games played on the Vita are the same as the Authentication on Smartphones [2]. In this study, a touch Playstation 4 version, there is no mobile specific content, or screen affixed to the back of a cell phone was used to enter any major change in game play. However, the DualShock a secure password by means of hidden gestures on the back 4 controller included with the Playstation 4 contains more of the device. A portion of the study showed users a four by input options than are available on the Playstation Vita. two grid of eight targets and instructed the users to touch Thus, the back of device touch screen has been used to mimic at location one and then drag to location two. The results these missing inputs to provide players the same gaming showed combined first point and second point accuracy to experience regardless of when playing on the Vita or on an be just over 70%. Other studies looked at back of device vs actual Playstation 4 using the DualShock 4 controller. front of device touch gestures [17]. This paper is looking at touch interactions of virtual buttons contained within video Commercial games utilizing the back of device for touch in- games, not gestures. put offer from one to eight virtual buttons on the back touch screen. This paper seeks to find limitations of utilizing the Back of device touch has also been used in implementing new back of device touch screen for gaming purposes. The com- styles of keyboards. A mechanical version of the concept, mercial uses of the back touch screen is analyzed in current RearType [9] physically attached a standard QWERTY key- Playstation Vita Games and Playstation 4 Games using Re- board to the back of a tablet screen. The keyboard was mote Play. A piece of software was developed to mimic the broken in half and each half was placed vertically along the current uses of the second touch screen as well as to measure sides of the tablet such that when it was held in landscape the possibilities of expanding its use. A user study evaluated mode, the keys were easily accessible with the fingers. Af- the software and the results are analyzed. ter a training session, it was found that RearType achieved an average of 15 words per minute. Sandwich Keyboard [8] 2. PREVIOUS WORK investigated the use of a keyboard input method where the thumbs provide input on the top touch screen, and the eight One of the reasons why back of device touch might be nec- remaining fingers type input from the back of device touch essary is that users may cover up important portions of the pad. Their method featured floating targets that adapted to screen with their finger as they attempt to navigate the a user’s grasp style. They found users could accurately type interface. Commonly known as the Fat Finger [11] issue, using this method and after training could reach speeds up other approaches besides back of device touch have been at- to and even exceeding traditional keyboard input methods. tempted, such as Shift [12], which enlarges the portion of the screen underneath the user’s finger and moves it away Different types of back touch screen interactions were inves- from the finger to allow the user to see what is beneath. tigated by Hasah et al. [3]. Their study looked at perfor- mance differences between relative and absolute back of de- Back of device touch is a fairly new concept in commercial vice cursor positioning. They found the relative positioning products, however its use has been evaluated in previous was significantly better performing than the absolute posi- research. One research project, Double-side Multi-touch In- tioning. Another approach to including a reference pointer put for Mobile Devices [10], investigated the use of touch device on the visible screen includes LucidTouch [16], where gestures on both the front and rear touch screens for new the visible screen appears semitransparent allowing the full interactive techniques to manipulate 3D objects. Their work outline of the hand behind the screen to be visible. This displayed circles representing the active touch points on the approach has also been proposed in a commercial android back of the device overlaid on the top video display in or- based smart phone [5]. For games, however, this may not be der to show users where their fingers were during gesturing. desirable as the cursor or hand skeleton may be distracting HybridTouch [15] uses back of device touch input to scroll a to players. map, while using the front touch screen for target selection. Yang et al. [18] also utilized both sides of the touch screen 3. BACK OF DEVICE TOUCH USE IN COM- in Dual-Surface Input research project. Their research com- pared acquisition times for front touch, back touch, and si- MERCIAL PRODUCTS multaneous dual surface touch when attempting to select To better understand how back of device touch is being used different sized targets. Their study contained a total of 1296 commercially, its use in the Playstation Vita is investigated. data points and found the average selection time to be 4.38 The Vita can be used to play games designed for the Vita seconds. The dual surface touch method performed better hardware, and it can also act as a controller for the Playsta- than the back of device only touch method and the back of tion 4 when running in remote play mode. Specific uses of device touch method outperformed the front of device shift each of these modes are analyzed and described below.