Don't get so tied up with planning that you just can't draw for planning.

I think that's what causes artists block.

If you get that, just draw some crazy stuff and have fun.

Some styles have such stairs as ready-made symbols, but if not you can save the gradient as a png with a transparent background and import it as an image (Insert File in the Draw menu), scale it to an appropriate size and paste it on top of the stairs.

There are other ways of doing the same thing, like creating a new symbol for yourself based on the existing one and editing the copy in a bitmap editor, or importing the gradient as a new symbol so you can reuse it anywhere you like, but if it is just a one-off and you don't have much experience with CC3 this is probably the fastest.

Here is a transparent png you can use if you don't have one already.

Create a new sheet just above the stairs and call it something appropriate, like STAIR SHADOW (just an example name), and import the image with that new sheet active. The reason for putting it on it's own sheet is so you can use sheet effects on that sheet if you wish without disturbing anything else in your map.

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EDIT: I should probably have mentioned earlier, but hopefully I'm not too late. When you insert a file you will need to keep the image file with the drawing from that point on, so best to start with it in the same folder. That is the one main drawback of using insert file.

Try adding a new sheet called DARKEN SHEET (or something similar) and put it between the sheets of the lower floor and upper floor. Then add a solid black polygon that covers the entire map and a Transparency sheet effect on that new sheet. Edit the Transparency effect and set the opacity to about 25% and see what you have. You can see the result on the right side of this floor. The central section is the original floor texture.

If you want to blur the view as well as darken it, call your new sheet BLUR SHEET (or something similar) and add a Blend Mode sheet effect (instead of the Transparency effect). set the BM effect to Linear Light mode and about 15% opacity. Then add a Blur sheet effect below that. You will only need a very tiny amount of blur. You can see the result of the BLUR SHEET on the left hand side of the map in the screen shot above.

Some people prefer to make a sheet that lightens the view rather than darkening it. If that is what you prefer just use Change Properties to turn the black polygons white. This is what both those sheets do with exactly the same sheet effects on them if all you do is change the black polygons to white.

These are caused by the nodes being too close together in a heavily fractalised polygon. Notice how they occur on the fractalised parts of the object rather than the simple straight line sections.

Undo or delete the new wall tracing and use the keyboard command SIMPLIFY, set a distance of about 0.25 (if that is a 5ft snap grid I can see), on the floor polygon. What this will do is remove any node that is only 0.25 feet or less in distance away from it's neighbour. Then either trace the wall shape again, or copy that polygon onto the WALLS sheet and hide the FLOORS sheet to change the properties on the WALLS sheet to create the new wall.

We are working hard on it. However, since my part in the whole thing is creating new assets for just a bit of it I can't really throw much light on anything else.