Level: 7th   

Casting Time: 1 action     

Range: 30 ft.

Components: V, S

Duration: concentration, up to 10 minutes

School: Transmutation

You magically alter the way gravity behaves around a target within range. If the target is an unwilling creature, they must succeed on a wisdom saving throw or suffer the effects. The target suffers one of the following effects of your choice. 

- Reduce Gravity. The targets weight is reduced by 500 pounds, to a minimum of 1 pound. If the target is a creature, anything that they are wearing is also affected. If the target becomes weightless and is a creature, they lose all of their speeds that aren't flying, but gain 10 feet of flying speed, unless they already have a flying speed, in which case the flying speed gains an additional 10 feet. 

- Shift Center. The targets point of gravity shifts 45 degrees towards one cardinal direction of your choice, or towards or away from you. Objects shifted in this way move 20 feet in the specified direction every round unless obstructed or held down. The object is treated as if it was twice as heavy as it pertains to pushing it against the specified direction, and is treated as half as heavy as it pertains for pushing it towards its specified direction. Creatures affected in this way gain twice as much speed moving in the specified direction, and have difficult terrain moving in any other direction. Creatures also have disadvantage against being knocked prone, and while prone, move 20 feet in the specified direction at the start of their turn unless held down, or until they end the turn on themselves. 

- Increase Gravity. The targets weight is doubled if they are an object. If the target is a creature, they gain weight equal to 1/4th their original weight. If this is equal to or exceeds their carrying capacity, they are immobilized. Otherwise, all speed is halved for that creature. All targets fall at double the speed they otherwise would. The used of the featherfall spell can cancel out this specific effect.

I think this mostly works... it seems kinda weak for a 7th level spell. I think a good comparison point is Reverse Gravity, another 7th level spell, which has a range of 100 feet and affects a very large area. I also feel like the wording on this is a bit overcomplicated and focuses on a lot of little details that aren't impactful to the game enough to bother with tracking them. Shift Center is far, far too wordy, in particular. I also think that a Wisdom Saving throw feels unusual for this... Wisdom Saving throws are intended more for spells that affect a character mentally in some way. I think a CON saving throw makes more sense for the specific effects this is creating.

I also think you should just include at the start that these weight changes affect a creature and anything worn or carried by them, that way you don't have to clarify that separately in each different option.

As for Increase Gravity... I don't think you need to separate doubled weight from objects and give creatures a different weight gain. Just make it double the weight of the target regardless, and ignore the carrying capacity detail. I also think the Featherfall detail is unnecessary... why would you design your 7th level spell so that it can be completely countered by a very common 1st level spell?

Can I cast center shift on myself? If I can, and have me move towards/away from me, do I just implode/explode? Also, what point on my body counts as "me"?

(Not a review at all, but I'm yoinking these and just want to know what you think)

Here I fixed it for you:

Alter Gravity (4th level Transmutation spell)  
Casting Time: 1 action;
Range: 60 ft;
Components: V, S
Duration: concentration, up to 10 minutes

Choose one target within range. The target may be a creature or an object of Huge size or smaller. The target must make a Constitution saving throw, on a failure you magically alter gravitational fields around them to cause one of the following effects on them and all objects they are wearing or carrying:

Reduce Gravity: The target's weight is reduced by 1,000 pounds, to a minimum of 0 (weightless). The target deals half damage with any Strength-based attack rolls, and if they become weightless they lose all their movement speeds other than flying. If the target can fly, their fly speed is doubled.

Increase Gravity: The target's weight is quadrupled. If this causes their carrying capacity to be exceeded then their movement speeds are reduced to 0, otherwise their movement speeds are halved for the duration, and they have disadvantage on Strength saving throws and are incapable of standing up if they are or become prone.

Rotate Gravity: You change the direction of gravity up to 90 degrees in a direction of your choice. The target falls at a speed of 50 ft per round in the chosen direction until it hits a solid object or creature, when it hits such an object or creature both it and what it struck take 1d6 bludgeoning damage per 10 ft it moved on this turn. Moving the creature / object in the opposite direction as this gravity requires 2 ft of movement to move 1 ft, while moving the creature / object towards the direction of this gravity moves it twice as far - this also affects the movement speeds of the creature itself.

Quote from Agilemind >>

Here I fixed it for you:

Alter Gravity (4th level Transmutation spell)  
Casting Time: 1 action;
Range: 60 ft;
Components: V, S
Duration: concentration, up to 10 minutes

Choose one target within range. The target may be a creature or an object of Huge size or smaller. The target must make a Constitution saving throw, on a failure you magically alter gravitational fields around them to cause one of the following effects on them and all objects they are wearing or carrying:

Reduce Gravity: The target's weight is reduced by 1,000 pounds, to a minimum of 0 (weightless). The target deals half damage with any Strength-based attack rolls, and if they become weightless they lose all their movement speeds other than flying. If the target can fly, their fly speed is doubled.

Increase Gravity: The target's weight is quadrupled. If this causes their carrying capacity to be exceeded then their movement speeds are reduced to 0, otherwise their movement speeds are halved for the duration, and they have disadvantage on Strength saving throws and are incapable of standing up if they are or become prone.

Rotate Gravity: You change the direction of gravity up to 90 degrees in a direction of your choice. The target falls at a speed of 50 ft per round in the chosen direction until it hits a solid object or creature, when it hits such an object or creature both it and what it struck take 1d6 bludgeoning damage per 10 ft it moved on this turn. Moving the creature / object in the opposite direction as this gravity requires 2 ft of movement to move 1 ft, while moving the creature / object towards the direction of this gravity moves it twice as far - this also affects the movement speeds of the creature itself.

 Thanks! This is perfect!

Thanks for the help, I credited in the now uploaded spell