shishagon

About This Game

Shishagon is a geometric logic puzzle that tasks you with placing numbers at the vertices of overlapping shapes so that each shape's vertex values sum to a specified target. The interlocking geometry creates a web of constraints where every number placement ripples through multiple shapes simultaneously. What begins as a simple arithmetic exercise quickly becomes a deep exercise in logical deduction as you balance competing requirements across shared vertices. Each puzzle has a single elegant solution waiting to be uncovered through careful reasoning. Challenge your mathematical intuition in this free browser game where geometry meets number logic.

How to Play shishagon

Each puzzle displays a set of geometric shapes — typically squares, triangles, or hexagons — that share vertices at their intersections. Some vertices already have numbers filled in, while others are empty and waiting for your input. Your goal is to place numbers in every empty vertex so that the values at the corners of each shape add up to the target sum shown for that shape. Click or tap an empty vertex to select it, then enter a number from the available set. The available numbers and the target sums are given at the start of each puzzle. Start by examining shapes that have the most pre-filled vertices, as they have the fewest unknowns to solve. If a shape has only one empty vertex, you can calculate its value directly by subtracting the known vertices from the target sum. Shared vertices are the most powerful constraint — when a vertex belongs to two or more shapes, the number you place there must satisfy all shapes simultaneously. Use this cross-referencing to narrow down possibilities. When multiple empty vertices remain, try different combinations and check for contradictions. If placing a certain number in one vertex forces an impossible situation in an adjacent shape, that number is eliminated. Work through the puzzle systematically, using each solved vertex to reduce possibilities in connected shapes until the entire grid is filled.

Highlights

• Geometric logic puzzles combining spatial reasoning with arithmetic
• Overlapping shapes with shared vertices creating interlocking constraints
• Increasing difficulty with more shapes and fewer pre-filled numbers
• Clean visual design with clear shape outlines and number displays
• Each puzzle has a unique solution solvable through pure logic
• Free browser game with no downloads or registration needed

Tips & Tricks for shishagon

• Solve shapes with only one empty vertex first — simple subtraction gives you the answer
• Focus on shared vertices since they must satisfy multiple shape sums simultaneously
• Use elimination by checking if a candidate number creates contradictions in connected shapes
• Write down possible numbers for each vertex and cross off impossibilities as you progress
• When stuck, look for the vertex shared by the most shapes — it has the tightest constraints