Mighty Gunvolt is free in Japan to players who download Azure Striker Gunvolt between August 20 and November 19, 2014. The same promotion is active for the North American release running three months starting on the day of release. Mighty Gunvolt was also offered out as a free download to all backers of the Mighty No. 9 kickstarter, as it also stars Beck, the main of that game.
Being that this is a crossover game, the story is an odd merging of the stories from Azure Strike Gunvolt, and Gal Gun, both games made by Inti Creates. The story is presented to the player by two screens of text, which are as follows, complete with broken English & spelling mistakes:
The other time, the other place: Experiments on humans started by the massive media group "Sumeragi" to audition for the next "Muse" idol. Their magic hand even reached female schools. Female students vanashed, and no new couples formed. Love was in a danger. "Gunvolt," it's the name who we call the only one to fight them. It's no accident he was involved in the troubles. Together with angel "Ekoro" and robot "Beck" he fights to free successivefuly occupied major city facilities.
Yes, those typos are in the game too.
Each of the three playable characters plays in a similar manner, with some unique abilities given to each. While all three can do the standard jumping and shooting, reminiscent of the 8-bit Mega Man games, only Gunvolt can do a double jump mid-air, Ekoro can briefly hover with her wings, and Beck is the only one able to slide dash under low objects. All levels have short alternative paths that only some of the characters will be able to reach thanks to their differing moves.
Each character also has a different charge-up attack. Gunvolt unleashes a powerful electric chain that he can move up and down in front of him, however he is unable to move while doing this. Beck can store a charge while moving that allows him to dash a short distance forward (different to his slide dash) that also damages enemies and can even be done mid-air. When Ekoro charges up her gun and fires it, a large heart shoots out that will "mark" an enemy. Now when she kills this enemy, instead of exploding, a halo appears over its head. The enemy is now an ally which will float behind her, shooting other enemies on screen until it takes enough damage to be destroyed once and for all.
Mighty Gunvolt has 5 levels: School, Train, Lab, Tower, and Mirror. Depending on which character you pick to play the game, the levels appear in a different order. Specifically, Ekoro starts in the school, which is an 8-bit recreation of a level from Gal Gun complete with giant tentacled plant monster. Beck and Gunvolt both start on the Train level.
Several stats are collected about each level, which can be viewed when selecteing a save file. The game tracks Hi Score, Fastest Time, Max Combo, and Clear Rate for each level, making score and time attacks a good reason to replay levels.