Pff that's a big topic with too many versions and too much code... :}
Well, search for the function where you place the mine, add a check at start for that variable...
PHP Code:
public place_mine(id)
{
if(g_bRoundEnded)
{
client_print(id, print_center, "You can't place mines after the round has ended")
return PLUGIN_HANDLED
}
//...
}
and add the other two roundstart/end functions... first search for them in the plugin and just add the vars there, if they are not there, copy them from my code

easy...
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