Echo Sounding (Arkai)

Echo Sounding is one of the daily deduction puzzles on Arkai, a small portal of free browser games that run with no account, no advertising and no third-party code. It went up on 21 September 2026.

Each day there are three grids, Easy, Medium and Hard, worked out from the date so every player gets the same ones. Easy is 6 by 6 with two hidden reflectors, Medium 7 by 7 with three, and Hard 8 by 8 with four. When you ping a cell, the grid answers with a single number: how many steps up, down and across it is from that cell to the nearest reflector. A zero means you hit one.

You switch to marking mode to place reflectors where the numbers say they must be, then press Check. Every ping costs one point and a wrong check costs two, and each grid has a par worked out by Arkai's own solver. Any set of marks the grid cannot tell apart from the real one counts as solved. Results can be shared without spoilers, a streak counts the days you play, and every earlier day stays playable from the arrows on the title screen.

It plays like a calm game of sonar: few rules, quick rounds, and each ping chosen to split the remaining possibilities. It suits players who like Minesweeper-style reasoning with fewer clicks, and it works with a mouse, a keyboard or touch.