System and IINA version:

• macOS 13.3.1
• IINA 1.3.1

Expected behavior:
IINA reduces animations if the user has enabled the macOS Reduce motion setting. From Apple's Human Interface Guidelines section Color and effects:

Play tightened animations when Reduce Motion is on. People can turn on Reduce Motion if they tend to get distracted or experience dizziness or nausea when viewing animations that include effects such as zooming, scaling, spinning, or peripheral motion. In response to this setting, you need to turn off or reduce animations that are known to cause problems (to learn more, see Responsive Design for Motion).

Actual behavior:
Disclosure triangles use a sliding animation when showing and hiding information.

Steps to reproduce:

• Start IINA
• Click on Settings… under the IINA menu
• The settings panel appears
• In the Behavior section click on the triangle next to Pause/resume when
• The nested settings slide into view

• MPV does not have this problem.

How often does this happen?
Every time.