Mental Flow

Mental Flow is the ability of a Magic user to be flexible in their casting of spells.

Reduced penalty from Automacity
It becomes increasingly hard to multi-task two or more spells at the same time, as the subconscious has to take care of continuing to cast the non-active spells. Better flow allows the magic user to multi-task spells in a way that it is easier on the mind, reducing this penalty and saving them on Mental Energy. A user with perfect mental flow can multi-task spells with no penalty at all, although this is unlikely.

Quicker switching of Spell Focus without penalty
Switching between spells is difficult, as it requires remembering the details of a spell and focusing on the new one. Casting more of the same spell helps the user get "in the zone", where they will particularly benefit from Spell Focus.

With low mental flow, the "switch speed" is prolonged and can be noticeable by feeling "mentally jammed" when trying to alternate between them. However, a very high mental flow reduces the time required to switch spell focus, which means the user can more easily do things like alternate between firing a fireball and then telekinetically grabbing an object to defend themselves with it.

However, attempting to cast two different spells by rapidly casting one and then the other is inefficient, as the magic user will incur the maximum of the 400% penalty on the second spell being used. So when firing Ice Spike from the left hand, it is ideal to wait a second or two before casting Fireball with the other hand.

With the worst mental flow, magic users can take up to 10 seconds to properly switch. With the best mental flow, their switch can go down to record times of 0.23 seconds.

Training
The primary way to train Mental Flow is to practice successfully alternating between spells without "mentally blocking" and to challenging oneself to successfully practice casting a spell while having a reasonable burden of other passive spells by using Automaticity. No skill is learnt by mentally blocking or fumbling, so it has to be taken slowly and gradually in order to learn, and done regularly until it feels effortless.

There are also non-magic ways to train mental flow, which is any worldly activity that involves multitasking. Being good at micromanaging and playing certain strategy video games can help increase mental flow. Even something a simple as driving a car while talking to someone can make its small contribution to helping the user gradually start being able to gracefully a variety of different spells.

Being creative also helps in mental flow, and doing anything that requires being "in the zone" help train this.

Examples
An extreme example of impressive mental flow is Whimpers, who is the only freak to beat Katie when it comes to mental flow. Whimpers, despite her harmless appearance, is highly studious in magic and practices it every day, and this flow did not come naturally. She also regularly plays video games that involve doing several things at the same time. To top that all off, one of Whimpers' Universal Concepts is Extreme Emotions, which causes her to feel everything with extreme intensely, allowing her to perform impressive feats such as turning into a bolt of lightning to shock and ricochet off a target, and then, merely a second after reforming, begin firing both Ice Spikes and Fire Balls from her left then right hand in a Spell Combo with an interval of 0.5 seconds while flying at the same time.

See Magic Stats for more stats that are inherent to a magic user's mind.