When I start the game, the title screen is too small compared to the rest of the window, which is black. This seems to be proportional to the window size. The buttons do not appear selected when you mouse over where they are, but rather where they would be if the title screen was at a normal size. This is my first launch of 13w38a.
Note: The white square in the screenshot is a result of the cursor being hidden when windows takes a screenshot.

EDIT: This is NOT a duplicate of MC-13661. The visual for the title screen is a square in this bug, but it is the default rectangle in MC-13661. Also, this only occurs at the title screen, other submenus of the title screen such as options and singleplayer are at their normal resolution. I'm not sure if this can be unmarked as resolved, but I would like it to be.