Counter-Strike, the famous multiplayer first-person shooter that amazed the world, is celebrating today, June 19, its 15th anniversary since the initial launch as a small Half-Life mod.

Counter-Strike was among the first true multiplayer sensations and it saw its first beta release on June 19, 1999, when two shooter fans, Minh "Gooseman" Le and Jess "Cliffe" Cliffe, decided to modify Valve's Half-Life game to create a whole new experience.

The new game was a hit and Valve quickly seized the initiative by hiring both Le and Cliffe, while purchasing the rights to the property. The whole process went by quite fast, and in 2000 the first retail release of Counter-Strike was revealed for the PC.

Since then, the experience became more and more complex, culminating with the hugely successful 1.6 iteration, which provided some of the most intense multiplayer shooting action on PC. Besides drawing in millions of players legally and even more illegally, the Counter-Strike 1.6 also created a vibrant eSports community, joining the ranks of Starcraft as staples of any gaming event.

Lots of professional teams joined in on the action and there were plenty of prizes being offered to the best ones.

In March, 2004, Valve released the experimental Counter-Strike: Condition Zero, which not only brought major changes to the multiplayer experience but also a series of single-player missions in which players were paired up against bots. As you can imagine, interest wasn't that great.

However, in November of that same year, Valve rolled out Counter-Strike: Source, a remastered version of the original experience in its new Source engine.

This was a hit, largely because of the stellar graphics for that period and the fact that lots of professional teams jumped to the new experience, bringing the eSports scene alongside it.

However, the player base was still split between 1.6 and Source, with many claiming that their favorite was the superior experience.

After many years, during which popularity decreased, Valve brought the franchise back with Counter-Strike: Global Offensive, in August of 2012, with the help of the Hidden Path team.

Unfortunately, after a not so impressive beta and a pretty buggy first release, many fans were reluctant to keep playing Global Offensive and it seemed that the franchise wasn't going to receive its stellar comeback.

However, Valve implemented the same community-driven design principles learned after Team Fortress 2 and started listening to feedback from regular players and former Counter-Strike professional teams. As a result, CS:GO became more and more popular.

The turning point for the new installment was the Arms Deal Update in 2013, which allowed players to earn customized weapon skins and trade or sell them using the Steam Market. Couple this with the growing number of user-made maps and skins on the Workshop, and the series came back to life.

Competitions have started receiving funds straight from Valve via the sale of special keys for weapon cases and the popularity of CS:GO has skyrocketed, becoming the second most played title on Steam, being overtaken only by the juggernaut that is Dota 2.

While Valve doesn't seemingly have anything planned for the anniversary of Counter-Strike, you can bet that the studio is working hard to improve CS:GO and keep its popularity rising.