Prototype Zones/Oil Ocean
From Sonic Retro
Oil Ocean Zone
The layout for this zone is much unlike compared to the final version. The most unique elements in this prototype level are wooden balls that were released from the ground if a switch is pressed. The ball doesn't hurt Sonic. In fact, Sonic can have a ride by standing on it. The velocity of the ball is fixed and Sonic cannot stop or push the ball.
A bigger version of the ball is also available in Sonic 1's Green Hill Zone. It's visible in debug mode, but you cannot place the object and see what it does.
Oil Ocean Zone plays music #81 in the prototype, or equivalently #08 in the final.
One detail that applies to both acts is that the sun behaves differently.