I ran the web build and played the first minute, up to the "Walk around a little" step (0 of 10 m), so this is only about the opening. The oversized flower and its long cast shadow next to Cordy sell the scale well. One thing I noticed: the key-hint list on the left is dimmed and sits right over the flower stem and leaves, so some of the rows were hard to read against the green. A slightly darker backing panel there might help. On the anthill, "atmospheric or frustrating" usually comes down to whether the player keeps a readable pool of light. A small warm light on Cordy with a soft falloff, plus a faint rim colour on walls and ant paths, keeps the dark feeling dark without losing navigation. For the scale question, a little depth-of-field blur on far foreground grass and a slight vignette often does more than adding objects.
Thanks for taking the time to play the opening! I'm really glad you checked it out and shared your thoughts. I'll definitely work on improving the readability of the key-hint list so it doesn't clash with the background. As for the depth-of-field effect, you can actually enable the blur in the settings menu!