I love the premise – an obstacle course with a rolling coin throughout the house is great.
However, I think you need to give us a little more control over the coin, especially turning left and right. It feels very stiff, so either I didn't manage to turn in time, or overdid it and the coin fell down.
I don't think I ever managed the pass more than two checkpoints in a row because it was hard to make sharp turns or stay on track once the boost kicked in. Thankfully, the checkpoints realign you, so after the first 90° turn, I only needed to go forward and turn a little between checkpoints. I think the coin should move similarly to a motorbike, just slower (e.g. see here https://youtu.be/CLGnRhsIgDw).
Additional details:
– As for the fountain, shouldn't it have water in it? Also, it's clear the pennies are mapped onto square tiles (or planes), because the textures don't align at the edges.
– Falling on the rug at the beginning makes the coin fall through it. The same with the floor around the fountain.
– You slow down too quickly and the kick from the boost is instant. I don't know how the slowing down is implemented, but in Unity, I'd recommend using 'AnimationCurve' ("[SerializeField] AnimationCurve curve" in code to make it editable from the Inspector). Make a fairly steep, but not instant slope at the beginning (the boost) up to 1 and then go gradually down to zero (slowing down).
https://docs.unity3d.com/ScriptReference/AnimationCurve.html
https://tinyurl.com/wp9y3ks
Multiply "curve.Evaluate( timeAfterBoost )" with the max speed and you'll have a much smoother speed increase/decrease.
– Everything is fully textured except the walls. Even if they're supposed to be solid-coloured, add a normal map and height map, so it doesn't look as flat and synthetic.
https://www.textures.com/search?q=plaster
Good luck with further development! :)