Alignment Guides and Snapping
Line elements up exactly while dragging, instead of landing a few pixels off.
What it adds
Live guide lines and snapping that align a dragged element to the edges, centres, and spacing of its neighbours.
What your agent is told to do
5
What your agent is told to do
5-
1
Snap to more than edges. Match left, right, top, bottom, horizontal centre, vertical centre, and equal spacing between three or more elements, and draw a guide for whichever match wins.
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2
Hold a modifier key to suspend snapping entirely for the duration of a drag, so an author who genuinely wants an element two pixels off the grid can place it.
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3
Compute the snap threshold in canvas coordinates, not screen pixels, so the pull feels the same at every zoom level. A fixed pixel threshold becomes unusable when zoomed out.
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4
Restrict the candidate set to elements that are visible and near the dragged element rather than testing every node in the document, or the drag will stutter on a long page.
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5
If the app already has drag-and-drop reordering, extend that drag layer rather than starting a second one. Do not run two independent drag implementations on the same canvas, because they will fight over pointer capture and produce dropped elements.
Edge cases it handles
8
Edge cases it handles
8- Snapping with no escape hatch is a trap. Provide a modifier key that disables it mid-drag, and make the disabled state visible so the author knows why the guides vanished.
- Testing every element on the canvas against every drag frame will drop frames on a page of any size. Limit candidates to nearby, visible elements and recompute the set at the start of the drag rather than on each frame.
- Aligning only to edges leaves elements that look wrong. Centre alignment and equal spacing between siblings are what authors actually reach for, so match those too and label the spacing guide with its measurement.
- When several targets fall inside the threshold at once, guides will flicker between them frame by frame. Pick the closest match and require a clear margin before switching, so the guide holds still.
- A snap threshold measured in screen pixels pulls far too hard when zoomed out and barely at all when zoomed in. Scale the threshold by the current zoom so the feel is constant.
- Guides drawn only as thin coloured lines are invisible to some users and against some backgrounds. Give them sufficient contrast on both light and dark canvases and announce the resulting alignment for keyboard users.
- Keyboard nudging must be able to reach the same aligned positions as dragging, otherwise anyone who does not use a pointer cannot align anything.
- Snapping must not silently move an element after the drag ends. The position the author released at, adjusted by the shown guide, is the position that gets saved.
Definition of done
8
Definition of done
8- Dragging shows guides for edge, centre, and equal-spacing alignment against nearby elements.
- A modifier key suspends snapping mid-drag and the interface shows it is suspended.
- The snap threshold scales with zoom so behaviour is consistent at any level.
- Guides stay stable when multiple targets are within range, with no flicker.
- Dragging stays smooth on a canvas with many elements.
- Guides are legible on light and dark canvases and keyboard nudging reaches the same positions.
- The feature matches the existing design system.
- No existing functionality is broken.
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Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/survey-builder
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Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/quiz-builder
How it works
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1
Copy the link
Grab the Markdown instruction URL for this feature.
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2
Give it to your AI
Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.
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3
It inspects, then implements
Your agent reads your existing app first, then adds the feature to fit it.
Works with your stack
These instructions are written to adapt. They tell the agent to detect your framework, match your existing design system, and reuse what you already have — rather than assuming a particular stack.
Need it tighter than that? Customize the feature and tell it exactly what you're running.