Uiua

Today's lesson: Never think that scanning the first 100 lines of input will give you a good understanding of it.

Part 2 is really messy and could probably be much simpler, but I couldn't get the logic straight in my head otherwise.

"L68 L30 R48 L5 R60 L55 L1 L99 R14 L82"
⊜⋕⊸≠@\s∧⍜⊡⋅@¯⊚⊸⌕"L"∧⍜⊡⋅@+⊚⊸⌕"R"
P₁ ← ⧻⊚=0\(◿100+)⊂50
P ← (
  ⊃(-×100×|/+)⌊÷100⌵⟜(⊸±) # Count and remove all over-rotations
  ⍉⊟↘¯1⊸(\(◿100+)⊂50)     # Take all positions and next moves.
  ▽⊸≡(≠0⊢)                # Ignore any starting from zero
  +/+↥⊃(<0|>100)≡/+       # Sum the pairs, check for passing zero.
)
P₂ ← +⊃P P₁
⊃(P₁|P₂)