(Very) Hard AND nice puzzles
The following list contains portal puzzles that have been rated as nice or very nice and that are difficult. These puzzles are recommended for experts - and allow some time to solve.
| Description | solved | Rating | |
|---|---|---|---|
 | Killer Kropki Sudoku by Willy Wonka (on 6. September 2020, 17:16) | 50 |  96 % |
| Irregular Antiking Sudoku by spxtr (on 15. September 2020, 01:45) | 24 | 96 % |
| Adamas by Polycarp (on 21. March 2021, 02:30) | 26 | 92 % |
| The River by wooferzfg (on 20. March 2022, 06:24) | 45 | 96 % |
| Peer Pressure by Cane_Puzzles (on 19. April 2026, 16:30) | 75 | 97 % |
| Frankenstein by zetamath (on 10. June 2025, 20:50) | 89 | 96 % |
| Tatlins Turm (Chaos Construction) by glum_hippo (on 22. January 2024, 22:52) | 57 | 95 % |
| Critical Mass (Renban Between Lines) by tallcat (on 13. March 2022, 21:18) | 72 | 96 % |
| U-Bahn with Empty Cells by Niverio (on 28. June 2024, 21:23) | 38 | 99 % |
| Hybrid Series #1: Pentominous Mid-Loop by Tyrgannus (on 11. January 2025, 11:32) | 33 | 98 % |
| Vampires by grkles (on 22. October 2021, 02:12) | 43 | 98 % |
| Acropora (Chaos Construction) by Agent (on 13. June 2023, 09:00) | 92 | 98 % |
| The Ultimate Prime Cages by Xenonetix (on 11. June 2024, 23:45) | 100 | 98 % |
| Post von den Außerirdischen by ibag (on 6. September 2014, 06:09) | 33 | 97 % |
| Japanisches Summen-Masyu by Uhu (on 20. June 2017, 17:56) | 48 | 99 % |
| Gaelic Knot by cam (on 27. September 2020, 20:08) | 14 | 93 % |
| Die Bahn ist auch auf dem Zylinder pünktlich ... by ibag (on 17. February 2021, 23:58) | 10 | 98 % |
| Antimagnetschlange by ibag (on 27. March 2021, 00:00) | 12 | 95 % |
| Hidden Identity Killers by Fluster (on 3. May 2021, 19:35) | 40 | 98 % |
| Kropki Sums by mathpesto (on 19. December 2021, 16:26) | 26 | 90 % |
