[Pierre-Marie Baty]

Regarding ServerActivate(), yes, it is called everytime a new map boots in. Actually a new map means a new server ; each time you change level (even in single player with level transitions), or force a level restart, in whatever manner you want, you will force a call to ServerDeactivate() immediately after the last StartFrame() in which the command was triggered, and a call to ServerActivate() immediately before the first StartFrame() of the new map.

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Why I'm reluctant to using HLTV messages is that HLTV is an "external" application using a not-so-well defined protocol, that changes very often. And the purpose of HLTV messages is not for notifying players of a round change, actually if this code is specific to a round change in CS it's pure coincidence ; and on the contrary, notifying clients of a change in the round timer is exactly the point of RoundTime messages...
</facultative>