Serious game ’underwater’
The setup of the serious game ’Underwater’ consists of a 3D printed ultrasound probe with a stylus pen inside and a touchpad connected to a laptop with the installed game. The setup was provided by the game manufacturer, but this company was not in any way involved in the design of the study or the conduction of the experiment. The game represents an underwater world where one is supposed to look for coins and to collect them’. The coins are collected by pointing the cursor exactly on the coin for at least one second. There is just one coin visible at any moment and coins have different levels of difficulty depending on where they are hidden, for example (partly) under objects. A level consists of 10 coins. The cursor on screen is moved by operating a simulated 3D printed probe across a touchpad using the same movements as a real ultrasound probe: rocking, tilting, sliding, and rotation. The intervention group started playing at level 1, and after completion they continued playing at other levels for approximately 20 min. They followed the protocol by playing level 1 for a second time. By repeating level 1 at a standardized level (meaning that the coins were hidden at the same spot), we were able to measure changes in time and in the quality of the movements, and therefore we could distinguish a learning curve within the game itself. An image of the setup, an in-game overview and visualization of the valid routes are provided in Fig. 