Offset: 0.5 (default)
STEP 1
Triggers when step reaches middle of viewport
Offset: 0.8
STEP 2
Triggers when step reaches 80% down viewport (near bottom)
Offset: 0.2
STEP 3
Triggers when step reaches 20% down viewport (near top)
Offset: 0.5 (default)
STEP 4
Triggers when step reaches middle of viewport