## 4 Discussion
On the other hand, if it is too easy, players might feel less challenged and become bored, which would cause players to focus less on the game and thus not improve their cognitive function at all. Additionally, if the game is too difficult, players might feel that the goal is unreachable, that there is a low chance of winning, and that there is a high chance of disappointment, which would lead to decreased concentration and thus no improvements in cognitive function [55; 93; 94]. Moreover, players can adjust or gradually increase the difficulty level during the game. Players might have increased their skill during the training period. They might feel that the original level is too easy, in which case players can gradually increase the difficulty level. Examples such as these might be what effectively leads to improvements in attention span and executive function. Pressure is another important game mechanic factor. The mixed repeated-measure ANOVA showed that there are significant differences between D-CAT (\(p<0.001\)), SAT (\(p<0.001\)), TMT-A (\(p<0.05\)), and TMT-B (\(p<0.001\)). The Yerkes-Dodson law states that appropriate and suitable pressure can increase performance, thereby improving attention span and execution ability. When the time is limited in the game, players must complete the goal of each game within the time limit. A suitable amount of time pressure can make the player focus more on the game, which can improve their attention span and executive function. The Yerkes-Dodson bell curve describes the relationship between pressure and performance. We can see that the best performance is at the highest middle point of the bell curve, which is a moderate amount of pressure [60; 95; 96; 97]. This might lead to suitable time pressure, which could enhance attention span and executive function. The time limit (in seconds) can be adjusted or gradually decreased during the game. The participant's skill might have increased in the training period. They might feel that the original time limit is too long, in which case they can decrease the time limit. The time limit can be adjusted to best fit each participant during the training. These might be what effectively leads to improvements in attention span and executive function. Competitive interaction is another important game mechanic factor. The mixed repeated-measure ANOVA showed that there are no significant differences between D-CAT (\(p>0.05\)), SAT (\(p>0.05\)), TMT-A (\(p>0.05\)), and TMT-B (\(p>0.05\)). Previous studies have shown that competition can increase performance for young people and adults, which includes the improvement of attention, physical effort, and motivation [65; 98; 99]. Not all digital games are suitable for the elderly. Therefore, a special design competitive game is necessary that can provide a positive experience and suitable for older players [100]. However, this experiment result shows that competition had a non-significant effect. There might be two reasons for this. Firstly, we used computer players (NPC, non-player character) as competitors. The competitor is controlled by a computer and is not human. Therefore, interactivity between humans might be different, and this might affect the effectiveness of the competition factor as human players might feel and act differently if they know that their competitors are computer players [101; 102; 103]. Another possible reason for this is the lack of communication with teammates or other competitors during the game [104; 105]. In a competition, there is communication, for example, between teammates; teamwork and inspiration are necessary, and players can chat with other competitors during a game to exchange information. These two reasons might explain why the competition factor had a non-significant effect in game training. There is an interaction effect between the difficulty factor and the pressure factor. The mixed repeated-measure ANOVA showed that there are significant differences between D-CAT (\(p<0.001\)), SAT (\(p<0.01\)), TMT-A (\(p<0.01\)), and TMT-B (\(p<0.05\)).