Compiling pingus error.

[bsdnewbie999]

I got these message while running scons.

scons: Reading SConscript files ...
/bin/sh: sdl-config: not found
OSError: 'sdl-config  --cflags --libs' exited 127:
  File "/home/keongpo/pingus-0.7.0/SConstruct", line 46:
    SConscript('src/SConscript')
  File "/usr/obj/i386/scons-0.97p0/fake-i386/usr/local/lib/scons-0.97/SCons/Script/SConscript.py", line 583:
    None
  File "/usr/obj/i386/scons-0.97p0/fake-i386/usr/local/lib/scons-0.97/SCons/Script/SConscript.py", line 520:
    None
  File "/usr/obj/i386/scons-0.97p0/fake-i386/usr/local/lib/scons-0.97/SCons/Script/SConscript.py", line 245:
    None
  File "/home/keongpo/pingus-0.7.0/src/SConscript", line 29:
    env.ParseConfig('sdl-config  --cflags --libs')
  File "/usr/obj/i386/scons-0.97p0/fake-i386/usr/local/lib/scons-0.97/SCons/Environment.py", line 1134:
    None
  File "/usr/obj/i386/scons-0.97p0/fake-i386/usr/local/lib/scons-0.97/SCons/Environment.py", line 473:
    None

What does it means? I have all the libraries installed.