Svyatoslav "HappyZerg" Vlasyuk, also known as "SlaViK", is a Zerg player from Ukraine, who is currently retired.
He reached A- on iccup ladder 
He was top5-6 at Ukraine's National WCG finals.
Wings of Liberty
HappyZerg joined Natus Vincere when they created their StarCraft II division. He mainly participated in weekly online tournaments, but in July 2011, Natus Vincere announced they had sent him in Korea in order to compete in GSL Code B. His first attempt to qualify for Code A wasn't successful, as he was eliminated early in the Code B bracket by PartinG.
On December 30, HappyZerg became teamless after Natus Vincere disbanded. He was picked-up by Guild of Imbalance on January 5, 2012. He joined FXO alongside other former Guild of Imbalance members when FXOpen parted ways with the Guild.
ESV TV Korean Weekly
On September 6, 2011, HappyZerg participated in the ESV TV Korean Weekly Season 1 Weekly 8. After taking down Cutter and Line, HappyZerg went on to face TaeJa. He was not able to advance any further after he lost to TaeJa by a score of 0-3 and fell in to the 3rd/4th place match. HappyZerg once again wasn't able to grab any more victories and had to settle for fourth place after losing to ByuN by a score of 0-2.
In 2012 he qualified for the Battle at Ministry of Win and for IPL5, but couldn't go because team refused to send him there.
Heart of the Swarm
On April 9, 2013, Natus Vincere announced a merger with FXO.Europe, resulting in all European players with the exception of the inactive Elbegast to play under Na'Vi. Despite being fairly successful, Na'Vi disbanded their SC2 team on 1 November 2013, but HappyZerg retained a sponsorship from ESFXtv.
|In Minor Tournaments|
|2013-10-09||1st||ESET Masters Season 3 Qualifier Cup #2||3 : 2||krr||$100|
|2013-07-24||1st||ESET Masters Season 2 Qualifier Cup #2||3 : 2||krr||$100|
|2013-07-10||1st||ESET Masters Season 2 Qualifier Cup #1||3 : 2||Revenge||$100|
|2013-03-24||2nd||Home Clash II||0 : 4||Welmu||€100|
|2012-11-27||2nd||GameCreds_Invitational||1 : 3||Snute||€100|
|Complete Results in any Tournament|
- 2012-03-23 | Interview with FXOSlavik on OGIC 2.0 by Team Virtuspro
- "Final DQs and Point Adjustments". TeamLiquid.net, 16 December 2009.
-  "iccup page"
- "Natus Vincere opens its StarCraft II division"
- "Na'Vi.HappyZerg to move to Korea!"
- Code B results
- "Natus Vincere disbands its StarCraft 2 squad". Navi-Gaming.com, 30 December 2011. TeamLiquid.net Forum thread
- HappyZerg: "imba.FXOpen.Slavik ^^". Twitter.com @HappySlavikk, 5 January 2012. TeamLiquid.net Forum thread
- sandr1x (2013-04-09). "Natus Vincere acquired new roster". navi-gaming.com/. Retrieved 2013-04-09.
- Fairon (2013-11-01). "Na`Vi.FXOpen disbands". teamliquid.net. Retrieved 2013-11-01.
- ESFX (2013-11-01). "HAPPYZERG ОСТАЕТСЯ!". esfxtv.com. Retrieved 2013-11-01.