After you turn on the last engine and hear the corresponding rumble, you need to find a lit up flashlight near the rocks, behind this flashlight is the entrance to the cave - namely, to the second level. In a couple of days I will make the transition to the next level more obvious and the game will be updated.
HOW-TO get to Level 2
Source: Steam Community (opens in a new tab)
Build and release context
Recorded Steam release date:
Within one calendar day of this post (UTC). The listed date does not establish an exact launch time.