gimp - Creating a tile for a word game

Please advise me how to use Gimp to create a tile for a word game like below:

I can see 2 rectangles with rounded corners - the outer one and then the one on the top.

Is the smaller rectangle filled with a linear gradient, where alpha changes from 1.0 on the top to the smaller value on the bottom?

How to create the "inner shadow" in the larger rectangle?

Answer

So in GIMP 2.8 you can do this:

1. Make a rectangular selection the size you want your button to be


2. Be sure to select rounded corners in the tool options


3. Save this selection to a channel, just to be sure you can retrieve it whenever you want


4. 
   
   

   Create a new layer for the button background, fill it with you base color

   
   


5. 
   

   Invert your selection in selection->invert

   
   


6. 
   

   Go to filters->light and shadow->drop shadow, and create your shadow, with 0 for X and Y offsets - there you are -a new layer with he exact shadow you wanted. : if you use the classic drop shadow script (not the GEGL based one in GIMP 2.9), it creates a shadow of the selection itself - in a new layer, above the current layer (it is different of the behavior when there is no selection)

   
   


7. 
   

   restore your ouriginal selection, create a new layer and make a white to black vertical gradient with the blend tool. Change this layers mode to "grain merge" and reduce its opacity until you are satisfied for the main blend of your button

   
   
   


8. create a new selection, smaller in order to create the Phong reflex - and on a new layer, create a blend from white to transparency for it. o adjust the transition from white to transparency, I prefer to use the colors->curves tool, operating on the Alpha channel of the reflex layer.

And there you are!