Here is a map of Gateways I made. I labeled things to mark what was needed to do each section.
Key: H = Health pick up J = Jump upgrade E = Extra Echo Ext = Extra time G = Rotation gun required (Gravity...) R = Mirrior required (cause without thinking I called it a reflector while making this...) T = Time Gun S = Size gun P = Basic Portal Gun F = Flash Light M = Multi Protal
Using this I created the following basic route thats decent, although maybe can be better.
Gateways Route:
Get H1 health pickup on the way down, can get all orbs using portals on the way. through portal and head up to get jump boost J1
After getting reflector Then go down to S+R get the 20 orbs, go up to SB to get 4 orbs and unlock door to catch that in the backtrack.
head down to H2, then head over to continue main goal.
After getting time gun go up and go through portal
Head though portal to E1, get Echo (use momentum with time portals) then back though portal.
Go to S+T1, get E2 and E3, go down to J2
Get Echo EE on the way to rotation gun.
Go get Rotation gun, get orbs on ceiling of on way back, go down elevator to get orbs and open shortcut, take portal to start to go get EXT1, the nearby echo, and time suit.
Head back to main area.
Teleport down to H3, get H3 orbs amd orbs at G1.
Then head to H4.
Go to unlock last portal.
Go get EXT2. Take portals back up to continue on toward multi gun.
Once you have multi gun go to M1, get orbs on the way and get the health on the way to M2. Then proceed to M3, take portals up to m4.
Then finish the game.
