Oh boy, what a journey this was. The short version of the story is - Sipho physics are now different - more squishy, wiggly and natural-feeling.

Just look at this Sipho segments individually moving in different directions!

New physics allow Zooids to have different Connection Stiffness parameter - something that controls how much deformation resistance Zooid has. Higher stiffness means less deformations and more similar behaviour to old physics. Lower stiffness means that connected Zooids will be more wiggly and Sipho will have more difficulty holding its shape. Current stats as of this patch are:

• All non-structure Zooids have 100% connection stiffness
  
• Saenus Chitin also has maximum stiffness. It should be de-facto the most stiff Zooid - When future physics tweaks allow us to have more stiffness Chitin stiffness will be increased. Currently it is as stiff as it can be
  
• Cra'Than Nervefiber has 80% stiffness
  
• Vagorian Peapod has 80% stiffness and a skill to toggle down to 10%
  
• Advena Zenoplate has 70% stiffness
  
• Buginis Splitter has 60% stiffness
  

The stiffness loss compared to old physics is somewhat acceptable for Siphos grown in Campaign mode - they don't usually reach the size where more stiffness would be needed. This won't be the case for super large Siphos saved in Aquarium. Some larger Siphos now might suffer from not being able to hold their shape:

This can be solved by using Chitin or adding more connections:
These improvements were long coming from the conception of Sipho. We once used built-in Unity 2D joints, but they have proven to be very unstable with more connections.

At some point we switched to shape-matching physics you have become familiar with - the algorithm would try to hold Sipho in shape that is defined by Layout. This worked for up to 4 by 4 Zooid sized Siphos. However, it had limitation of not understanding limbs - larger Siphos would feel box-like and deform somewhat unintuitively.

Hopefully these new physics will make Sipho stand out even more from similar games, such as shipbuilders and other rigid-body simulation games. Having quite rigid and box-like creatures didn't feel as organic and live as we want Sipho to feel.

To iron out all issues and provide as much variety as possible physics might get tweaked in the future - we want to provide as many creative compositions as possible and allow you to make creature you wish to play with.

Just look how happy he is stretching those limbs!

And for the most curious, please have a changelog! Read bottom-to-top:
Version 0.8.0f2

• Optimize Zooid food eating check
  
• Add flail launch force over time
  
• Make procedural generation of Cra'Than Boss 3 more robust
  

Version 0.8.0f1

• Tweak Layout Info panel
  
• Fix Whirlpool NaN on spawn
  
• Fix Growth Ghosts being updated in between growth states
  
• Add ChargeUpButton and use it for Layout deletion button
  
• Tweak skill UI font so Q is more visible
  
• Deselect growth element when tooltip is shown in tutorial
  
• Do not show center text in Tutorial as it obstructs other text
  
• Fix typo in tutorial
  
• Fix wrong info for skill rebind key
  
• Extrapolate positions and rotations from velocity when adding new body to deformable
  
• Add wider margins for growth camera
  
• Do not automatically regrow Zooids which neighbors are too far away. Apply force to bring them together
  
• Fully stiffen Zooid connections when they are close enough
  
• Grow Zooids with connections initially relaxed for far away neighbors to reduce immediate forces
  
• Use last seen alive neighbour position to display dead Zooid ghosts
  
• Fix NaN center of Mass and Thrust when Sipho dies
  
• Regrow zooids next to their alive neighbors rather than at undeformed position
  
• Place new zooids locally according to their neighbor position
  
• Add Mass and Movement Force stat icons to Growth Mode. Clicking them toggles display of their areas
  
• Recalculate Center of Mass and Center of Thrust on Sipho to support stat display in Growth Mode
  
• Recalculate Sipho volatile stats on Zooid reposition
  
• Move whole Sipho if center of mass is outside of area of trust - fixes unbalanced Siphos getting stuck on rocks while trying to turn
  
• Prevent Sprite renderers without sprite to be cloned. Remove dummy sprite renderer from Grabber connection
  
• Do not update Growth menu in Fixed Update - should reduce lagspike when entering growth mode
  
• Override Sipho stiffness to undeform when entering growth mode
  
• Allow setting custom save/data path with -datapath launch argument
  
• Move Relax skill onto Peapods, make them originally stiffer
  
• Projectile weapons apply their knockback force over several frames to avoid breaking physics simulation with large impulses
  
• Fix certain Buginis boss layout Zooid positions being off-grid
  
• Whirlpools always break obstacles and decorations
  
• Add soft body connection stiffness parameter to Zooids