“SMOD” is a single player Half-Life2 mod. "The_Author" is the creator of this fascinating mod, which was drawn up in late 2004. Mainly made for Japanese players, The Author seems to refer to SMOD as "The HL2 mod of Japan".
The mod is played in original Half-Life 2 story and adds various new weapons, humor, and more to create a more enjoyable single player experience. But, that's not all of SMOD. SMOD is designed for customization and made to fit the players personal enjoyment.