What the first screen is showing
Each daily round puts two cut-outs on the same ground line. The black one is the reference. Its label already states the measurement this board uses, in metres and in feet, so you are not hunting for a hidden fact about the reference. The white one is the thing you are sizing. It starts at a guess that is deliberately not the answer. Your work is to change that white shape until it looks right beside the black one.
The question at the top names the target and the axis. Tall, long, across, and area are not the same question. A tower is judged by height. A whale is judged by length. A country drawn as an area is judged by area, and the stage shows the square root of that area so two regions can share a picture without one of them vanishing. Read the axis before you touch the slider. A careful eye on the wrong axis still scores nothing useful.
The black cut-out is already to scale
The reference is not a mascot. It is drawn from the same measurement the label quotes. On this board a large adult blue whale is 27 metres long, and a full-size school bus is 12 metres bumper to bumper. If those two ever share a round, the whale should look a little more than twice the bus, because 27 divided by 12 is 2.25. You do not need that arithmetic to play. You need the picture. The arithmetic is what the score uses after you commit.
References are chosen so the ratio to the target stays inside a playable band, wider than a toss-up and narrower than a joke. The slider itself is wider than that on purpose. It runs from a small fraction of the reference up to many times the reference, on a logarithmic scale. Equal slides are equal ratios, not equal metres. That is why a small nudge near a tiny object feels as serious as a small nudge near a ship: both are percentage moves.
How to change the white silhouette
Drag across the stage, use the slider under the grid, or press the arrow keys. Right and up grow the guess. Left and down shrink it. The plus and minus buttons take a slightly larger step than one arrow press. Zoom out when the target is so large that it leaves the grid, and zoom in when you are comparing two modest objects and the difference lives in a small gap. The grip on the white shape shows which axis you are changing. A height grip sits on top. A length grip sits on the side.
Nothing is submitted until you lock in. You can scrub back and forth as long as you like. The hint under the slider is a reminder, not a timer. On a phone the same gesture works on the stage itself: slide to resize, then use the lock button. The daily board does not expire in the middle of a round. It expires at midnight in your own time zone, for everyone on that calendar date.
What the red outline is doing
Lock in and the true silhouette is drawn over your guess in red. If you were large, the red shape sits inside the white one. If you were small, the red shape sticks out past it. The label grows a second line with the measurement this board actually uses. That line is the grade. The red is not a penalty colour and it is not a stamp of failure. It is the tape, shown in the same picture as your eye.
The fact under the reveal tells you which version of the object you were judging. The Statue of Liberty on this board is ground to torch with the pedestal, about 93 metres. The figure alone is much shorter, and people who remember the statue without the stone base will lock in low. The Eiffel Tower is taken to the tip of the antennas, about 330 metres. Big Ben is the tower, not the bell. Those sentences are part of the game. They stop a pedantic argument from pretending to be a wrong answer.
The score follows the ratio
Points come from the ratio of your guess to the truth, using whichever way is larger. Half the true size and double the true size are the same kind of miss, and both score 45 on this board. Within 6 percent still scores 100. A miss of about 12 percent scores 90. About 20 percent scores 78. A third off, a ratio of four to three, scores 62. Triple scores 30. Five times off, or worse, scores 0. Between those marks the score slides with the logarithm of the ratio, so the penalty grows smoothly instead of falling off a cliff at one magic percentage.
A perfect round is 100 before the day's weights. Five rounds use the weights one, one, two, three, and three. The last two rounds are worth triple, which is why a casual first guess and a careful last guess are not the same decision. The maximum for a five-round day is 1,000. Unlimited pairs are scored the same way per lock-in, without that five-round weighting, because there is no shared finish line.
A shared day, then a private streak
The daily five are picked from the date in your time zone. Friends on the same local date get the same pairs, in the same order, as long as they are both on the mixed board. A category filter changes the shelf, so a sports day and a mixed day are different puzzles even on the same date. Finish the five and the result stays in this browser. There is no account. Clearing site data clears the streak. That is deliberate: the game does not keep a profile of you on a server.
The answers page stays closed for today until you finish, or until you choose to look. Looking is allowed. It spends the surprise. The measurements themselves are rounded public figures from encyclopedias, sports rules, and manufacturer specs. They are good enough for an eye, and they are labeled when a famous object has more than one honest height. They are not a surveying certificate.