A friend and I recently became interested the 15-puzzle. It's simple to solve, but there's surprising depth to solving it efficiently and quickly.
Unfortunately, existing apps for the 15-puzzle are slow and filled with advertisements. Taxicab on the other hand is a 15-puzzle for speedrunners. In addition to a stopwatch and color-coded design, it uses hovering and dragging as input methods as opposed to clicking or tapping, which is significantly faster.
This first ship is the base experience needed for speedrunners. Future versions will incorporate history, statistics, multiplayer, and more.