Design
The Age Is Just a Parameter design
One birthday joke for people who write code, on a tee and on a mug.
The design is laid out like a settings screen. AGE IS JUST A PARAMETER runs across the top, with PARAMETER on a teal highlight inside square brackets, the way a variable looks in a code editor, and a slider underneath reads STILL WITHIN ACCEPTABLE RANGE. The slider shows no number, so the joke suits any birthday. The tee and the mug carry the same artwork, and on the mug it is printed on both sides.