Rooms that change each round? Help Please?

I once read a Half-Life 1 tutorial about this. At the start of each
round walls appear somewhere and somewhere els they dissappear. Sou you
could make a Hostage and defuse map in one for example, each round with
a new objective. A room with hostages and one with a bombspot. One
closed bij a wall another open.

Can this be done in HL2? If so how?

Have you even tried doing it the same way???

I remember a CS map where the CT and T switched positions every round. Perhaps they used the same or a similar technique.

The problem is, I cant find that tutorial anywhere. Any help would be appreciated...

It can be done, just set it up to where it will enable or disable the
bomb target (maybe), set up a logic_auto and set it to maybe "on CT
spawn" disable bomb target 1.

You could use the same technique used in cs_havana (i dont know exactly how it was done).

Are you talking about Gollum's GMDM2 tutorials? (Which is WAY more badass then changing once per round!)