Hi!
I give u a capture zone, which runs on a timer that is only active when a player is in the zone. If the timer is running and a player from the other team enters, the timer is stopped.
The counter i used has 0-12 as min/max so each team has 6 seconds and 1 second remains for neutral state.
I also added indicators for the timer as you can see in the pictures, that all have 6 steps towards each color and 1 neutral.
The buildwalls are removed for a team if the have control, but if it is neutral when phase changes, both walls will appear.
The logic_case is for indicators and logic_compare is for buildwalls
Beware of the indicators, each of them are 13 sets of grouped brushes.
There is also 2 multiple_trigger in same place, as well a 3 lights over the capture zone.
I added a rar file with bsp and vmf so you can see how i made it.
Haven't bug tested it much yet, so if you find any flaws post it here.
I hope you like it
Edit: Update - Now it works