I've played it. If you got stuck at the same point I did then....
After you get the green power up there's a room on the upper level with a cross-shaped block with water on both sides and a pole sticking out the top. To the right of that, underneath the ledge, there's a hidden switch that raises that platform.
After getting the blue power up go right, then on the screen with the flashing house warp, climb up a screen and double jump your way across to the left. It's tricky, but doable.
First screen: Press Down where it's glowing, it will open a tunnel.
There's a save there.
Second screen: That jump can look hard at first glance, but it's not.
You have to jump and double jump left.
You will touch the side of the platform, and you will be able to climb up.
I guess you just have to hold the Up arrow when you touch it