CREATIVE NOTES / CODING & PLAYFUL LEARNING
A 5% Type Is Not a 5% Card: Two-Stage Selection in Monica’s Play
If a guide says “SGR: 5%”, does every SGR design have a 5% chance? Monica’s Play is a new virtual card album on the portfolio website of Hong Kong primary pupil Zhan Yining, also known as Monica. Its two-stage selection rule provides a concrete way to read percentages. This is an editorial analysis of the recorded rules and code, rather than Monica’s own account of designing the project or a claim that she developed it independently.
First ask what the 5% describes
The current album has six types—R, SR, SSR, LSR, SGR and TR—with four designs in each, making twenty-four designs. Their type probabilities per card are 40%, 25%, 16%, 8%, 5% and 6%, which total 100%. The 5% describes selecting the SGR type for one card. All four SGR designs share that chance. It is neither the chance of each design nor a promise that a pack will contain SGR.
Two steps explain the division by four
The rule first selects a type using those weights, then selects one of that type’s four designs with equal chances. A particular SGR design therefore has a probability of 5% × 1/4 = 1.25%. A particular TR design has 6% × 1/4 = 1.5%. Adding the four SGR designs’ individual 1.25% chances returns the original 5%. Giving every design 5% would count the type’s whole chance four times.
Picture four hundred equal squares
Imagine four hundred equal squares on paper. The SGR type occupies twenty because 20 ÷ 400 = 5%. Share those twenty squares equally among four designs: each receives five, and 5 ÷ 400 = 1.25%. TR occupies twenty-four squares, giving each of its four designs six, or 6 ÷ 400 = 1.5%. This diagram explains the rule. It does not mean the game contains a stock of four hundred cards, or that four hundred selections must reproduce these exact counts.
Three cards are not three turns through the types
A pack contains three cards. The rule repeats both steps for each card, permits duplicates and has no guaranteed rarity. An R card first does not exclude R from the next selection. Missing SGR earlier does not automatically increase its later chance. “5% each time” cannot be translated as “exactly once in every twenty selections”. A small set of outcomes differing from the stated proportions does not by itself prove an error, and there is no need to keep opening packs to make the counts match. All artwork can already be browsed directly.
A small exercise without opening a pack
Here is an optional reader exercise: without opening a pack, calculate the chance of one particular SSR design and then one particular R design. Both types currently contain four designs, so the answers are 16% ÷ 4 = 4% and 40% ÷ 4 = 10%. Now ask whether division by four would still work if a future type contained five designs. You would first need to check the new count and whether the designs still had equal chances. Understanding which group is selected first and which design comes next is more useful than memorising an isolated percentage.
Two more questions
Does each of the twenty-four designs have a 1-in-24 chance?
No. The six types have different weights. Equal chances apply to the four designs within one type: a particular R design has 10%, while a particular SGR design has 1.25%.
Does a card become more likely after it fails to appear?
Not under the current independent-selection rule, which has no guarantee mechanism. Earlier outcomes do not automatically change the next card’s type weights or design selection.
Explore the project
Prepared by the portfolio editorial team from the project rules and existing code, with AI-assisted writing and translation. Calculations and suggested activities are not Monica’s quotations or personal records. Portfolio inclusion does not mean she independently completed every design or line of code. The album contains AI-assisted fan illustrations of existing characters; this article does not reproduce them.