The feasibility of electroencephalography (EEG) analysis in evaluating mental workload of gaming was studied by carrying out a proof-of-concept type experiment on a set of EEG recordings, with a bespoke tool developed for the purpose. The EEG recordings (20 recordings in total) that were used in the experiment had been acquired by groups of students and staff of Tampere University during n-back gaming sessions, as part of course projects. The ratio of theta and alpha power, calculated over the EEG signal segments that were time-locked to game events, was selected as EEG metrics for mental load evaluation. Also, Phase Locking Value (PLV) was calculated for all pairs of EEG channels to assess the change in phase synchronization with the increasing difficulty level of the game. Wilcoxon rank-sum test was used to compare the metrics between the levels of the game (from 1-back to 4-back). The rank-sum test results revealed that the theta-alpha power ratio calculated from the frontal derivations Fp1 and Fp2 performed as a confident indicator for the evaluation and comparison of mental load. Also, phase locking between EEG derivations was found to become stronger with the increasing difficulty level of the game, especially in the case of channel pairs where the electrodes were located at opposite hemispheres.