Complex sentence: Each melting Lab is split into 16 initial stages, and each stage is represented by a test-tube, but if players do exceptionally well in one melting Lab in particular, they may unlock a secret 17th stage.
Split into simpler sentences: Each melting Lab is split into 16 initial stages, and each stage is represented by a test-tube. If players do exceptionally well in one melting Lab in particular, they may unlock a secret 17th stage.