Allowing the player to move in 3D space within 2D art is extremely difficult. Early on we did a lot of experimentation to decide between using 3D physics or faked 3D physics. Both have their limitations, creating optical illusions where either gameplay doesn't match the visual representation or vice versa.
Tall objects, for example, are problematic because as they get taller their collision needs to reach other heights. In this screenshot, the tall vine object actually would want to have a collider at each height we support. If we used 3D space instead, we could just provide a 3D collider and be done.
Making the object appear more top-down helps clean the collision up, but removes some of the character of the sprite. Given that Unity has made a lot of 2D tiling improvements since we began development, we might do it differently if we were to start over tomorrow.
Feel free to reach out and ask questions if you're interested in learning more about our approach. We always like to share our solutions but don't want to go too far into the weeds with everyone.
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