I used blue, waterclear LEDs that I bought some time ago. Unfortunately, these LEDs break when they get too warm, and I fried several of the LEDs while soldering them to the board... In the end, I got it all done just in time.
This is the finished case, closed. The case itself is a lot larger than strictly necessary, but I quite like it this way.
The case opened. From top to bottom: the board with the LEDs, the board with the microcontroller and the transistors, a small plate with the buttons and the powersocket.
The board with the LEDs. As in the first version, each LED has its own resistor. The rows are tied together, and is sourced directly from the microcontroller. The columns are fed into transistors.
The board with the microcontroller. Again, it's a 16F628A, running at 4MHz. In the first version, the transistors were placed on the LED board, but this time I placed them on the controller board. This makes for a much neater arrangement and easier soldering. OK, so there are a lot of wires running on this board, that that doesn't bother me overly much. Soldering this was much, much easier than the first version, and it looks neater.
Here you see what they mean with 'waterclear': the LEDs have no color of themselves. You can't see what color they are until they're turned on.
The clock running. The LEDs are quite bright -- I might need to build an automatic dimmer for the night, so that babarage isn't kept awake by the light. Not all the LEDs are equally bright if you view it from an angle -- some LEDs are placed at a slight angle...
Still, I'm quite pleased with the end-result! I also like the combination of the white case and the blue LEDs, it's literally a cool effect!