People often say that it was better back in the day... well, now it's time to put this theory to a test. Make a creative save using only 19 original TPT elements in this new "back to the roots" contest!

Contest rules:
1. Your save must use only the following 19 elements, which were present in the 2010 TPT version:

WATR, FIRE, LAVA, NITR, GAS, GOO, METL, SNOW, NEUT, DUST, OIL, STNE, GUN, CLNE, C-4, ICE, SPRK, WOOD, PLUT.

2. You can't hide newer elements inside particle properties or with layering, so ICE with ctype ACID isn't allowed. If a new element is created with a reaction, for example, WATR boiling to WTRV, then it's fine.

3. All walls (even new ones), signs and streamlines are allowed.

4. Ambient heat, Newtonian gravity and other simulation options are allowed. Deco is not allowed.

5. To participate in the contest, your save must have the tag "backroots". Only saves uploaded after 1st of November 2026 can participate.

Any save theme is allowed in this contest, it can be a calculator, reactor, factory, etc. The only requirement is that at the start the save must have only allowed elements, but when unpaused it can generate whatever elements you want. In particular, you don't have to set simulation options to "legacy" to participate in the contest. As always, submitting several saves is allowed.

Here's an example save:

Layering is allowed, but hiding new elements under old ones isn't. So, for example, TTAN alloys aren't allowed.

"but when unpaused it can generate whatever elements you want" 

can I get clarification on what exactly this means

Basically what Aklego-777 said, see also the example with WATR and WTRV in my post. The save itself must contain only allowed elements at the start, but when you unpause it, various reactions may happen which will create new elements such as WTRV, SMKE, URAN etc.