Here is a list of all files with brief descriptions:

[detail level 12345]

lib
common
defines
TWI_defines.h	Macro definitions for TWI/I2C communication flags and operations
drawing
elements.h
enums
TWI_enums.h	Enumerations for TWI/I2C interface modes, operations, acknowledgment, and error codes
macros
PORT_macros.h	Macro definitions for port operations
STRING_macros.h	Helper macros for stringification in C preprocessor
numbers
datatypes.h	Enumeration definitions for various numerical data types
radix.h	Enumeration for numerical radix options
hal
avr
twi
twi.c	Source file with implementation of hardware TWI/I2C functions and macros
twi.h	Header file with declarations and macros for hardware TWI/I2C
twi_soft
twi_soft.c	Source file with implementation of software TWI/I2C functions and macros
twi_soft.h	Header file with declarations and macros for software TWI/I2C
avr0
system
system.c	Source file with implementation of system clock initialization
system.h	Header file with declarations and macros for system clock configuration
twi
twi.c	Source file with implementation of hardware TWI/I2C functions and macros
twi.h	Header file with declarations and macros for hardware TWI/I2C
twi_soft
twi_soft.c	Source file with implementation of software TWI/I2C functions and macros
twi_soft.h	Header file with declarations and macros for software TWI/I2C
oled
font
font.c	Source file containing the ASCII font table data and character lookup function for text rendering
font.h	Header file for font handling and character bitmap retrieval
frame
frame.c	Source file implementing frame management and drawing functions for OLED display
frame.h	Header file for frame handling on OLED display
tty
tty.c	Source file with implementation of TTY text output interface on OLED display
tty.h	Header file for TTY interface - text output on OLED display
oled.c	Source file with implementation of OLED display driver functions
oled.h	Header file for OLED display control via hardware or software TWI/I2C