So you think you know box shadows?

Performance and Browser Differences

• Many commenters report the demos run “butter smooth” on a range of hardware: old AMD desktops, mid‑range Android phones, recent MacBooks, and various Pixels/Samsungs.
• Several report serious issues on Safari (Mac and iPad): slideshow‑like frame rates, freezing, and loss of scrolling, even on high‑end iPads.
• On some M2/M3 Macs, Firefox struggles with certain animations while Chrome runs smoothly.
• Overall theme: performance is excellent in many environments but fragile across browsers, with Safari most often blamed.

GPU Rendering, Transparency, and Overdraw

• Discussion explains that transparency complicates GPU batching: opaque draws can use depth buffering and arbitrary ordering, while transparent draws require correct painter’s order.
• Overdraw is highlighted as the main cost: transparent rendering often processes many pixels that end up partially or fully obscured.
• Memory bandwidth on mobile devices is flagged as a key limit, especially when transparency forces repeated framebuffer reads/writes.
• Some contrast browser engines with game engines: browsers try to minimize re‑rasterization and layer count, whereas games redraw everything each frame and can assume full hardware control.

Alternatives: Canvas and Other Techniques

• Several note that everything in the article could be done more easily and efficiently with <canvas> or WebGL.
• Others argue box‑shadow is used here precisely because it’s absurd and funny, not because it’s practical.
• Canvas is called out as faster but worse for accessibility and more suited to fixed‑size regions.

Rounded Rectangles and SDFs

• Commenters connect the “cheap rounded boxes” remark to signed distance fields and classic rounded‑rect hacks from early GUI systems.
• Modern shader‑based approaches for fast rounded rectangle shadows are referenced.

Accessibility and Practical Use

• Multiple voices stress that such heavy box‑shadow usage should not be used in production; it can cause lag and resource waste.
• Canvas and complex box‑shadow UIs are both seen as weak from an accessibility standpoint.

Cultural, Nostalgic, and Personal Reactions

• Many express strong enthusiasm for the creativity and “impractical hacking,” likening it to early‑2000s web experiments.
• Some reminisce about Winamp visualizers and lament that modern streaming players lack similarly rich visual experiences.
• A side discussion touches on learning graphics/GPU programming later in a career, trade‑offs between “fun” game work and better‑paid CRUD work, and the tension between “building the future” and valuing personal time.