Make tests easy to run
Factorize applyUntilStable
Refactor applyGravity (readability and small perf improvements)
Refactor applyMerging (readability and small perf improvements)
Refactor applyMerging (readability and small perf improvements)
Add a test for a bug
Fix bug of two-blocks horizontal jelly (and solve level 2!)
One jelly pushes another (and solve level 3!)