E4 improves upon the previous titles by making true on the promise of the PSP E3. Mizuguchi's trademark music synesthesia style was merely cosmetic in that title, with almost no interactivity between the music and gameplay. E4 is different, however. As if taking a cue from Everyday Shooter, the explosions now add to the musical tapestry of the game, as they'll add an interesting and catchy beat to the music playing in the background. Detonating at the top of a beat will make the resulting blast even more powerful, so internalizing the music will only add to the gameplay experience.
E4 also adds a new shield system that encourages players to pick up power-ups as quickly as possible before they become vulnerable once again. The balance created by the new shield system creates a much faster-paced game than before, one where players will opt to trigger explosions more frequently -- it also makes the game a lot more accessible than the PSP title, which was somewhat notorious for its difficulty.