NOTE: 8 bit = 256 colors, 16 bit = 65,536 colors.
When operating in tile mode, you can use up to four backgrounds each controlled independently using different maps and tiles. By default they are rendered 3,2,1,0 meaning that background 0 would be displayed over 3.
The GBA supports hardware rendered sprites that can either share one 256 color palette or there can be up to 16 different 16 color palettes that a sprite can use. Sprite palettes are separate from the screen palette. There can be up to 128 different sprites ranging in size from 8x8 to 64x64 pixels. Modes 0,1,2 have 32 KB of sprite memory while Modes 3,4,5 have 16 KB.
The GBA has 6 sound channels. 4 are standard music channels similar to the GB/GBC. The other two are allow direct sound sampling.
I recommend you go to The Audio Advance for more info on the GBA sound system.
Well, that's it for Day 1. We didn't go into too much detail on the hardware. Again, I will cover what is necessary as we go through the tutorial.
For more information on GBA hardware, I would recommend you check out the following sites:
CowBite Virtual Hardware Specifications
Mappy VM SDK 0.1
Discuss Day 1