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Print the following:

• Character index within CHARGEN (0..511)
• Offset within CHARGEN (index * 8)
• Current absolute address

Add a sprite that shows a normal sized preview of the currently shown character.
Simply putting the screen code in screen memory is not an option as we cannot show all the characters in CHARGEN as display is limited to 256 characters and is affected by the chosen character set: graphics/uppercase or lowercase/uppercase.
The extended background color text mode limits this even further as only the first 64 characters are available.

In the updatepreview subroutine of pixie the zero page address pointer is increased using inc and the overflow of the lower byte is checked using the carry flag.
However the inc instruction does not affect the carry flag (only N and Z) thus the high byte would never be increased. The routine only functions as the pointer points to sprite block 13 ($0340-$037f) which address area does not cross the page boundary.
In order to fix this the zero flag must be queried after the lower address byte has been increased.

Check and remove unused labels like

• linprt
• clrlin

So that the numbers align:

left - current; right - proposed layout

Display the available commands (movement keys, etc.) on the screen.

Enter a number to view the character at that specific index (0-511).

If the user enters a character index and exits the program then the cursor is white:

At location GDCOL ($0287) I found $81 or $01 probably causing the cursor to become white. If you enter something it turns light blue as it should.
At COLOR ($0286) the value is correct: $0e for light blue.

Each character in CHARGEN is made up of 8 bytes of data. The bits of each byte describe the pixels of a single row.

Add the possibility to save the sprite data to disk.

As we are using extended color background text mode only the first 64 shapes in the screen code table can be used.
This means that if we use the lowercase/uppercase character set then we do not have capital letters as printing "A" will result in printing "a" with another background color.

Currently printing a "capital" uses the same background color in bgcol1 as the character view for the bits that are on. Maybe use another color register for the on bits.
Subroutine prtline prints $60 (space with bgcol1) for the on bits and $a0 (space with bgcol2) for the 0 bits.

Subroutine togglepixel:

For instance in row 7 column 17 the screen address calculation does not work as expected.
PLOT returns with $04f0 in PNT and $10 in PNTR. The routine adds PNTR to the low byte of PNT but does not take any overflow into account.

Printing the following texts:

• index
• offset
• address
• preview

means to first position the cursor then simply print the text.

Currently there are separate subroutines for this that do the same and only differ in the string pointer and the x,y coordinates.

Add a multi-color sprite logo with the program title printed on screen.