Google seems to be in the process of rolling out some changes to the presentation of the web version of the Google Play Store. Most notably, the changes affect the way screenshots, reviews, and the device compatibility list are presented. Unlike some Google design changes this one seems to already largely be in effect and so there is a good chance the new design is live for those who check now.
In terms of the screenshots, the most obviously change is when an image is now clicked it appears more prominently. The interface makes use of lightbox to bring the image front and center with the background darkened, resulting in much improved viewing experience. For reference, the before and after looks can be compared in the image above and below. This change does come with some comprises, however. First of which is not all images are equal with some filling up the screen more than others. This is the case from app to app and for images for the same app. Likewise, while in expanded view the user is easily able to scroll through the gallery, when scrolling when not in an expanded view the entire process is now significantly slower. As before, images jumped from one to the next when the user clicked on the corresponding arrow, now users have to either hold down the arrow or repeatedly click until the current image moves to the next.
As for the reviews and device compatibility list (the drop-down tab) both of these have been significantly cleaned up through a greater use of a white background. The reviews in particular have changed significantly as now when a user clicks on "Read All Reviews" the user is redirected to a dedicated page where all reviews are viewable in a infinite scroll manner. Resulting in the web version of the Google Play Store now responding in much the same way as the Android app does. Which presumably is the point here with these changes. As while they do clean up the appearance of the Play Store for the web in general, they do also adopt more of a universal cross-platform look. There are also some more minor changes that might be worth noting, such as the option to filter reviews by device type and also the install count has changed from a range to a minimum value.