The red record button turns darker red while recording. That is the only indication that recording is in progress, and can be easy to miss, especially on touch screen when the pressing finger covers the button.
Some feedback from a user:
I did not notice the darkening, but now that you mention it, I can see it. Seems not to be enough: [... we] were initially often unsure whether a recording was ongoing or not, also because of internet delay the appearance of the green arrow represented the created recording can take a small while to appear.
I would say that the button could show some animation/activity, such as pulsing. The recorder and play elements create a gray "corona" when hovering over them, which is fine, and the play button pulses once when you press it; for me, a similar visual feedback could be given constantly while recording.
And keep in mind that on a cell-phone, the fingertip will cover the button itself, so the visual signal must be somewhat larger.
The red record button turns darker red while recording. That is the only indication that recording is in progress, and can be easy to miss, especially on touch screen when the pressing finger covers the button.
Some feedback from a user: