When a Queue Becomes Readable

A traffic puzzle can fit many vehicles into a small screen and still make its next decision readable. The important question is what the player can distinguish at a glance. A parked vehicle, a vehicle already travelling along the road, and an opening in a queue need different visual treatment. Colour alone cannot explain all three states.
I maintain a Car Sort walkthrough site. Looking through a contact sheet from a Level 162 recording, I was struck by how much information came from the board's arrangement before any written instructions were added. Three vertical bays occupy the top, while horizontal rows sit below the bend in the road. That separation gives the player two places to inspect without turning the whole screen into an undifferentiated grid.

Make the route visible before the choice

The road connects those areas through a conspicuous right-hand bend. In the sampled frames, vehicles on that route occupy a different visual space from the parked rows. That is useful design information: the player can inspect traffic already in motion separately from vehicles awaiting a decision.
A walkthrough annotation should preserve this distinction. An arrow pointing at a parked car explains where to act, but a second arrow across the road could be mistaken for another instruction. I would use a short label for the selected vehicle and reserve route markings for explaining its destination. The two annotations answer different questions, so they should not compete visually.

Empty space needs an explanation

Later frames show rows that are much easier to read because fewer vehicles remain in front of the coloured groups. The revealing change is sometimes the space that has opened, rather than the vehicle that just moved. Cropping tightly around a tap would lose that evidence.
This matters when comparing a player's board with a guide. A familiar colour is a weak match on its own. The surrounding row, its access to the road, and the vehicles still occupying neighbouring positions provide a more specific comparison. The Car Sort traffic-order guide is the project I maintain for these walkthroughs; I use the visible board state as the starting point for interpreting a route, rather than treating a colour name as a complete instruction.

A counter is part of the interface

The sampled screen also includes a small counter with a denominator of sixteen. Its value changes between the selected moments. The images establish that the counter is present, but they do not by themselves establish the meaning of every increment or reset. A guide should explain a counter only after checking it against the actual sequence.
That is a useful restraint for interface analysis too. A number can be legible and still leave its meaning uncertain. Designers can reduce that uncertainty with a stable label or a brief introduction, especially when a change in the number influences the next decision.

Keep the explanation proportional

The contact sheet contains replay-labelled frames as well as earlier views. I would separate those sequences before drawing any step-by-step arrows. Otherwise, two visually similar boards could be joined into a route that the recording never actually followed.
Readable puzzle design and readable explanation meet at this point: both help someone identify the current state before choosing an action. A clear road, distinct parking areas, and carefully explained counters give the player something concrete to compare. Adding more instructions is useful only when those instructions resolve an ambiguity the board leaves open.