There are hints below, read beyond the controls section at your own risk (of spoilers).

Controls

Click + Drag on an existing joint to build

Ctrl + Drag to move a joint

Shift + Click to delete a joint

Hints

Level 1: Follow the dotted lines

Level 2: Build a bridge that dips down

Level 3: Make the bridge in two (longer) segments connected by only a single joint

Level 4: Have two subsequent pivot points connected to the bottom joints

Level 5: Make part of the bridge get crushed when the top block expands