(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 | |
|---|---|---|---|
 | The inconvenient square root (chaos construction) by filuta (on 19. December 2021, 13:30) | 37 |  99 % |
| Missile Command by Xenonetix (on 13. July 2022, 00:44) | 34 | 96 % |
| Belagerungsturm by Myxo (on 22. September 2024, 14:12) | 39 | 98 % |
| Nuriquarium Sudoku by Jay Dyer (on 26. January 2023, 12:46) | 55 | 93 % |
| Wichtel 2020 (4): Memo an den Weihnachtsmann by wichtel (on 27. April 2021, 02:02) | 16 | 98 % |
| Heart Breaker (Arrow Sudoku) by FryTheGuy (on 27. May 2021, 03:36) | 18 | 93 % |
| Crypto Lying Japanese Cavescraper Ring for polar by KNT (on 20. December 2022, 02:44) | 37 | 99 % |
| Sailing by ThePedallingPianist (on 15. February 2023, 00:18) | 22 | 98 % |
| SubwaYY to H... ? [Secret Satan #2] by Christounet (on 4. January 2025, 16:24) | 17 | 100 % |
| Cyclone (Secret Satan 4-in-1 Sudoku/Shading/Loop Hybrid) by MaizeGator (on 5. January 2025, 03:30) | 20 | 97 % |
| ...the rest is for you to discover by aqjhs (on 18. July 2025, 08:39) | 18 | 97 % |
| The S-Cell Miracle by Niverio (on 22. May 2022, 16:40) | 56 | 97 % |
| Roller Coaster Yin Yang Cipher by Piatato (on 26. December 2022, 11:26) | 32 | 100 % |
| Unique Japanese Sum Sudoku by tesseralis (on 28. July 2023, 05:34) | 80 | 97 % |
| Runway (Killer sudoku with maximum totals + arrows) by Qodec (on 6. October 2024, 19:06) | 79 | 95 % |
| Chaos Construction: Increasing Path by KNT (on 3. October 2022, 23:31) | 103 | 96 % |
| Schrödinger's Deconstruction by mathpesto (on 19. June 2022, 13:57) | 49 | 98 % |
| Crux by Jay Dyer (on 22. October 2023, 16:09) | 89 | 97 % |
| Chaos In Frankfurt! (Secret Satan 2023) by Niverio (on 1. January 2024, 17:25) | 38 | 100 % |
| Region Geometry X by kolot (on 2. June 2022, 00:28) | 44 | 99 % |
