Here is the full list of all 30 World of Contraptions achievements.
Complete all tutorials
Upload a level created by you to the Steam Workshop
Subscribe and download a level created by another player in the Steam Workshop
Upload a contraption created by you to the Steam Workshop
Subscriber and download a contraption created by another player from the Steam Workshop
Complete sandbox mountain level
Complete the sandbox mountain level by collecting at least all silver stars
Complete the sandbox mountain level by collecting at least all gold stars
Complete the sandbox mountain level by collecting all silver and gold stars
Complete all levels of the easy groups in the main campaign
Complete all levels of easy groups in the main campaign by collecting at least all silver stars
Complete all levels of the easy groups in the main campaign by collecting at least all gold stars
Complete all easy group levels in the main campaign by collecting all silver and gold stars
Complete all levels of the medium groups in the main campaign
Complete all levels of medium groups in the main campaign by collecting at least all silver stars
Complete all levels of the medium groups in the main campaign by collecting at least all gold stars
Complete all medium group levels in the main campaign by collecting all silver and gold stars
Complete all levels of the hard groups in the main campaign
Complete all levels of hard groups in the main campaign by collecting at least all silver stars
Complete all levels of the hard groups in the main campaign by collecting at least all gold stars
Complete all hard group levels in the main campaign by collecting all silver and gold stars
Complete all levels of the extreme groups in the main campaign
Complete all levels of extreme groups in the main campaign by collecting at least all silver stars
Complete all levels of the extreme groups in the main campaign by collecting at least all gold stars
Complete all extreme group levels in the main campaign by collecting all silver and gold stars
Complete all levels of the main campaign
Complete all levels of the main campaign by collecting at least all silver stars
Complete all levels of the main campaign by collecting at least all gold stars
Complete all levels of the main campaign by collecting all silver and gold stars
Complete a level of the main campaign for the first time