The Engineering Challenge

~ build it so it doesn't break! ~

Your job

Real engineers know that materials expand when hot and contract when cold. If a long bridge has no expansion gaps, it will buckle and crack on a hot day. But if it has too many gaps, the road becomes bumpy and expensive to build.

Place expansion joints in the right spots so the structure survives an entire winter-to-summer cycle without cracking. Click anywhere on the structure to drop in a joint. Click an existing joint to remove it.

Interactive thermal-expansion game. Use a mouse to click on the structure to place or remove expansion joints, then press Run the Test.
structure
Bridge
joints placed
0
temperature
15°C

How to play

the rules
  • Click on the structure to add an expansion joint where you click
  • Click an existing joint to remove it
  • Press "Run the Test!" to cycle from neutral → freezing → boiling → neutral
  • If any joint runs out of room (gap reaches 0), the structure cracks — fail!
  • Pass with the fewest joints possible to earn 3 stars ⭐⭐⭐
the science behind it
Every segment of the structure tries to grow longer in heat and shrink in cold. With the bridge ends anchored, that growth has to go somewhere — into the expansion joints. More joints means each segment is shorter, so each segment expands less, so each gap doesn't need to be as wide. It's a balancing act between safety (more joints) and a smooth ride (fewer joints).
← back to expansion lesson → next: forces (pushes & pulls)
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