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Infinite puzzles. Adaptive difficulty. No forced ads.
Letter Challenge
✗ No — here's why it's impossible
No — this shape has too many odd-degree vertices to be drawn in one stroke.
| Vertices | 6 |
| Edges | 5 |
| Odd-degree vertices | 4 |
| Euler path possible? | ✗ No |
| Euler circuit? | ✗ No |
| Difficulty | Hard |
A letter e has 4 odd-degree vertices. The odd/even vertex rule states that a graph can only be drawn in one stroke if it has 0 or 2 odd-degree vertices. Since this shape has 4, it cannot be drawn in one stroke.
Learn the complete odd/even vertex rule →
If you enjoyed figuring out whether a letter e can be drawn without lifting your pen, you'll love One Stroke: Line Puzzle Game. It generates infinite one-stroke puzzles — every single one is guaranteed solvable, and the difficulty adapts to your skill level.
It also adds a twist: tiles flip color (black ↔ white) as you draw, and when a full row becomes one color, it clears — like Tetris meets one-stroke drawing.
Read more: Best One-Stroke Games Ranked · How to Play · Download
No — a letter e cannot be drawn without lifting your pencil. It has 4 odd-degree vertices, but you need 0 or 2 for a continuous path to exist. However, you can practice similar challenges that ARE solvable in one-stroke puzzle games.
Yes — count the points where an odd number of lines meet ("odd vertices"). If there are 0 odd vertices, start anywhere. If there are 2, start at one of them. If there are more than 2, the puzzle is impossible. This rule works for every one-stroke challenge.
One Stroke: Line Puzzle Game by CyberGame Limited is free on iPhone with infinite procedurally generated puzzles, adaptive difficulty, no forced ads, and a unique color-flipping mechanic. It's only 14.5 MB and works completely offline.
Infinite puzzles. Adaptive difficulty. No forced ads.