Logic Masters Deutschland e.V.

This is probably between 2 and 3 in difficulty and should be fairly approachable without prior experience of consecutive sum lines. If anyone enjoys this solve, they may wish to try other puzzles using the same ruleset:

• Contrail
• Increments
• Decrements
• A Dynamic Line

Rules:

• Normal sudoku rules apply.
  
• German Whispers: Cells connected by a green line must have difference of at least 5.
  
• Consecutive Sum Lines: Within each 3x3 box, the sum of digits along a contiguous red line segment is consecutive with the sum along the red line segment in any box it directly connects to. If a line re-enters a box, each contiguous segment is a separate sum which may be different in value if permitted by other rules. For example, in box 1, the sum of [R1C1, R2C2, R3C2] and the value of R3C3 may be different but each differs from the value of R4C2 by exactly 1.
  i.e. Red lines behave like region sum lines, but the sum increases or decreases by 1 whenever the line crosses into a box.

Below is a simple 4x4 example to illustrate the rule set.

F-Puzzles link: https://f-puzzles.com/?id=yvl4zy6g
SudokuPad link: https://tinyurl.com/2sre7m3m