# Development and Validation of a System for Game Control Based on a Force Plate
## 5 Results and Discussion
The result of the third calibration step was determining the threshold for initiating the simulation of pressing the SPACE key or clicking the left mouse button. After the game control system was calibrated, it was ready to be used for testing. For the purpose of system testing, the following thresholds were used from Tables 1 and 2: \(x_{TH}=40\), \(y_{TH}=40\), and \(a_{TH}=4.35\). The \(x_{TH}\) and \(y_{TH}\) thresholds were determined empirically (by conducing experiments), while the \(a_{TH}\) threshold was the mean value of all the acceleration maximums found in the third calibration step. Figure 15 shows the simulation of pressing the RIGHT, LEFT, UP, and DOWN keyboard keys. Of note is that the player's CoP in the local frame {G} was in the [\(-100\), \(100\)] range. The graph in Figure 15 shows that when \({}^{G}y_{CoP}>40\), pressing the UP key was simulated. If \({}^{G}y_{CoP}<-40\), then pressing the DOWN button was simulated. This test shows that the system for game control correctly simulated pressing the RIGHT, LEFT, UP, and DOWN keyboard keys according to the conditions in Table 1.  
Figure 14: Player CoM acceleration measurements along the \(z\) axis during the performance of impulse half squats (third step of system calibration). Figure 16 shows the simulation of pressing the SPACE keyboard key. It is visible that pressing the SPACE key was only simulated when the player's CoM acceleration along the \(z\) axis during an impulse half squat was greater than the defined threshold of 4.35 m/s\({}^{2}\). Furthermore, the impulse half squats that had an acceleration of less than 4.35 m/s\({}^{2}\) did not trigger the defined threshold, and in those cases, pressing the SPACE key was not simulated. This test shows that the system for game control correctly simulated pressing the SPACE keyboard key according to the conditions in Table 1.  
Figure 17 shows a simulation of moving the mouse cursor on a screen with a horizontal resolution \(X_{RES}\) = 1920 and vertical resolution \(Y_{RES}\) = 1080. The red frame shows the screen size of 1920 \(\times\) 1080 px. The transformation of the player's CoP position in the local frame [G] to the screen local frame was carried out according to Equation (13). Of note is the fact that the cursor position moved within the defined screen resolution. The procedure used to trigger the simulation of clicking the left mouse button was the same as the process used for the SPACE key. Figures 11-17 show the successful calibration procedure of the system for game control based on a force plate. After successfully conducting the system calibration procedure, the system was ready to be used for the purpose of game control. Figure 16: Simulating pressing the SPACE keyboard key. Figure 15: Simulating pressing the RIGHT, LEFT, UP, and DOWN keyboard keys. The system calibration and testing are also demonstrated in video form on YouTube [24]. The first part of the video shows the placement of the player on the force plate, followed by a successful calibration of the system for game control based on a force plate. Each system calibration step described in the diagram in Figure 4 resulted in parameters that were then used to control the game. The second part of the video shows successful control of a randomly chosen online game using a prototype of the game control system based on a force plate. The player who participated in the experiment rated the game experience as very good.