The next sentence is false. The previous sentence is true.
Youtube
Workshop Collections
Artwork [infinitelite.deviantart.com]

Chairs. What's that chair doing there? Why is there a pile of chairs? And why did I see chairs going through the vac tubes? So one time I put a chair in an empty corridor. Then another somewhere else. Then perhaps a pile of them in a room. It ended up being somewhat of a mapping trademark. So don't be surprised if you see a chair chillin'. Or, maybe hanging from the rafters. Besides, you might need a rest after all that testing.
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VMF demo maps for the Hammer Editor.
Open them with Hammer and you can use them to get an idea how things work. Some of them include some extra goodies to study. Some have the prefab brushes I use such as Test Chamber Door openings that the door fits into. Feel free to use those. Or save as a prefab.

Wheatley Demo. Includes camera and monitor
https://drive.google.com/file/d/19oDliCEM0sZre-Muz4rVUKnEynAvht8g/view?usp=sharing

Fizzler Demo. Different size fizzlers plus description.
https://drive.google.com/drive/folders/1z7an8ZEe6wmLpj3Nc80G9GBTzTZsZrv_?usp=sharing

Tractor Beam, Laser and Laser Collector. Plus how to reverse polarity.
https://drive.google.com/file/d/1OffoPjRduK7pJc5TbGi6rosR8a5iY18B/view?usp=sharing

AND Gate Buttons Demo. This is the method I use for 2 buttons for 1 door in AND configuration.
https://drive.google.com/file/d/1-4F5xe8617NnCaDUNE0QAP_wBQqD50V4/view?usp=sharing

Bomb Dispenser Demo. Press the button and the tube rotates and starts dropping bombs.
https://drive.google.com/file/d/1YEnHC4NNiaOKY-ZT7r04rG8IWmFWSsvu/view?usp=sharing

Conveyor Belt Demo. Also includes crushers at the end of the conveyor line.
https://drive.google.com/file/d/1WeDp8L79dX3Y7gsgeGMQPxMseL5Y1LNk/view?usp=sharing

World Portal Demo. A VMF demo using linked_portal_doors and teleport entities.
Past, present and future. World portals linking to future overgrown/decayed. Teleportation to past reconstruct. Includes other useful things if you want to make mind-bending maps
https://drive.google.com/file/d/1-rC5DabQUVCr0pnXMv34oAsMZ84n8HiM/view?usp=sharing

Catapult Demo. A basic catapult but it's bi-directional. Straight forward and straight up when triggered.
https://drive.google.com/file/d/1hThkhToek9EOup0qKYkzvLqQ6Zdp3xKx/view?usp=sharing