Spellstrike

A spellstrike, known in Japan as a magical break, is an action command used to increase the strength of a party member's spell in Magical Starsign.

Magical Starsign
A spellstrike is performed by tapping on a party member while they are casting a spell, specifically at the moment that the sparkle effects of the casting disappear. If the spell is offensive, this will cause it to deal 1.5x damage. If the spell is a healing spell, this will cause it to recover 1.5x the amount of hit points or magic points it would otherwise.

While a spellstrike can be performed for the neutral spell celestial swap, it has no effect on the magic point drain when moving planets. Similarly, the input can be performed but does not have an effect on stat-boosting spells such as minty freshness.