Mainly tested on:
  Box
    - Pentium 166MHz PC.
  OS
    - Linux 2.0.35 i586
  Make
    - GNU Make 3.76.1
  C compiler
    - gcc 2.7.2.3
  Ruby
    - ruby 1.4.2 (1999-09-18) [i586-linux]
  Gtk+
    - Gtk+-1.2.6
  Imlib
    - 1.9.4
  BGM ;-)
    - `Mint To Kutibue' (by Mayumi IIZUKA)

Result of `time make' (CFLAGS='-pipe -O2 -g -Wall') on the above environment:
user   355.980 sec
system  21.960 sec
total  377.940 sec

Other environments on which tested:
