Each [ card ] can have a gradient applied using the nine point position matrix. The class is in the format 'gradient-' so if you add a class gradient-0 this would start from the bottom full gradient to transparent. Class values are in 45degree increments, e.g. .gradient-45, .gradient-90, .gradient-135. The degrees are round the clockface.
It is useful to be able to control the gradient colour for certain effects. This can be done by adding the modifier class .gradient-surface, .gradient-light & .gradient-dark. It's important to know in this instance gradient-light and gradient-dark refer to the colour scheme mode of the page. This means that light may actually be a darker contrast and vice versa.