Error: gamemaker gravity not working

What's Causing This Error

The error 'gamemaker gravity not working' in GameMaker Studio typically isn't an error message generated by the engine itself but rather an indication that gravity isn't being applied to an instance as expected. There are several potential causes for this behavior:

1. Gravity Values Are Not Set: The gravity and gravity_direction variables may not have been properly initialized or set within the instance that requires gravity.
2. Not Applying Gravity: Gravity needs to be applied using the vspeed or phy_speed_y property (depending on whether you're using the physics engine). If gravity values are set but not applied, the instance won't show any gravitational effects.
3. Incorrect Event Usage: The logic to apply gravity might be placed in an incorrect event, which is not being called during gameplay.
4. Conflicting Movement Code: Other movement code may be overriding the gravity effect, such as manually setting the y position on each step without considering gravity.
5. Physics World Issues: If using the built-in physics engine, ensure that the world has been created correctly and that the object has a physics property assigned.
6. Collision Overriding: Sometimes, collisions can reset the vspeed or phy_speed_y to zero, inadvertently preventing gravity from taking effect.

Solution - Here's How To Resolve It

To resolve the issue with gravity not working in GameMaker, consider the following solutions based on the potential causes:

1. Initialize Gravity Variables: Ensure that you initialize gravity and gravity_direction for your instance, possibly in the Create event:

   gravity = 0.5;
   gravity_direction = 270; // Assuming 270 is downward in your game

2. Apply Gravity: Update the vertical speed of the object to include gravity. In the Step event:

   vspeed += gravity;

   Or for the physics engine:

   phy_speed_y += lengthdir_y(gravity, gravity_direction);

3. Review Events: Make sure your gravity code is in the appropriate event, like the Step event, so it executes regularly.

4. Check Conflicting Code: Look through your code for any other adjustments to the y position or vspeed/phy_speed_y and reconcile those with your gravity code.

5. Configure Physics Properly: If using the physics engine, ensure all necessary physics properties are setup: create a physics world and assign physics properties to your objects.

6. Manage Collisions: In collision events that might affect vertical movement, make sure to account for gravity after resolving the collision.

If these checks do not solve the problem, it could be beneficial to place debug messages or use breakpoints to track the changes in the related variables at runtime, helping to pinpoint exactly where the issue lies.