Here is the full list of all 23 Clockwork achievements.
Play the Game for Two Hours
Play the Game
Finish the First Level
Finish Act 01
Finish Act 02
Finish Act 03
Finish the Game in One Session
Beat the First Boss without Dying
Die during the Act 1 Boss Fight
Beat the Final Boss without Dying
Die during the Act 3 Boss Fight
Solve a Puzzle with a Shamblebot
Kill a Shambler
Solve a Puzzle with a Box
Solve a Puzzle with a Sentry
Die 5 times in one level
Idle for 5 Minutes
Place a Portal
Use a Portal
Control Milli
Fix a Leg
Fix the Generator
Solve a Puzzle using a Time Remnant