Price fluctuation

References

1. ^ abIn the USA GameCube release (GAFE01_00, ACreTeam/ac-decomp), Kabu_decide_price_sunday sets the Sunday price to 100 × (1 + (r − 0.5) × 0.6), with r from fqrand in [0, 1), stored in a 16-bit integer: a whole number of bells from 70 to 130 (computed with f32 rounding). 130 comes only from the generator's top value, 1 − 2⁻²³, where 1.29999995 × 100 rounds to 130.0; that is one 23-bit draw in 2²³. A decompiler's comment gives the range as [70, 129].CodeACreTeam/ac-decomprevised
   How we know

   164#define TRADE_MARKET_SUNDAY_BASE_PRICE 100.0f
   ⋮
   169 * Prices will always been in the range of [70, 129] bells.
   ⋮
   172  f32 price = 1.0f + (fqrand() - 0.5f) * 0.6f;
   173  Save_Set(kabu_price_schedule.daily_price[lbRTC_SUNDAY], price * TRADE_MARKET_SUNDAY_BASE_PRICE); /* [0.7, 1.3) * 100.0f = [70, 130) bells */
   

   17    __qrand_itemp = __qrand_idum >> 9 | 0x3F800000;
   ⋮
   19    return *(float*)&__qrand_itemp - 1.0f;
   

   Checked against the evidence by its author, an AI model, 2026-10-22.

   Revised after a check by a second AI model, 2026-10-22.

   In the claim ledger

2. ^ abIn the USA GameCube release of Animal Crossing (GAFE01_00, the build ACreTeam/ac-decomp rebuilds), the turnip market keeps one price per weekday, a 7-entry daily_price table indexed Sunday (0) to Saturday (6), with the market type and the date the table was set. The turnip seller (kabuPeddler) charges the Sunday entry per turnip, times 10, 50, or 100 for a bag. The shop buys at Kabu_get_price, the entry for the clock's current weekday, times 10, 50, or 100 for a bag and 0 for a spoiled turnip. The price doesn't change within a day.CodeACreTeam/ac-decomp
   How we know

   26  /* 0x00 */ u16 daily_price[lbRTC_WEEKDAYS_MAX];
   27  /* 0x0E */ u16 trade_market;
   28  /* 0x10 */ lbRTC_time_c update_time;
   

   46  lbRTC_SUNDAY = lbRTC_WEEKDAYS_BEGIN,
   47  lbRTC_MONDAY,
   

   205  return Save_Get(kabu_price_schedule.daily_price[Common_Get(time.rtc_time.weekday)]);
   

   81    static int sell_sum[aEKPD_KABU_TYPE_NUM] = { 10, 50, 100, 0 };
   ⋮
   93            price = Save_Get(kabu_price_schedule).daily_price[lbRTC_SUNDAY] * sell_sum[kabuPeddler->kabu_type];
   

   2986    static int kabu_sum[4] = { 10, 50, 100, 0 };
   ⋮
   2999            value += Kabu_get_price() * kabu_sum[item - ITM_KABU_START] * counter;
   

   2780#define ITM_KABU_SPOILED (ITM_KABU_START + 3)
   

   Checked against the evidence by its author, an AI model, 2026-10-22.

   Checked by a second AI model, 2026-10-22.

   In the claim ledger

3. ^ abIn the USA GameCube release (GAFE01_00, ACreTeam/ac-decomp), Kabu_decide_trade_market picks the week's market type from last week's with one fqrand draw: after type A, A 50%, B 30%, C 20%; after type B, A 60%, B 20%, C 20%; after type C, A 60%, B 30%, C 10%. The tables hold the A and B odds and C takes the rest. The decompilers' comments call A a spike trend, B random, and C falling.CodeACreTeam/ac-decomp
   How we know

   12  Kabu_TRADE_MARKET_TYPE_START,
   ⋮
   14  Kabu_TRADE_MARKET_TYPE_A = Kabu_TRADE_MARKET_TYPE_START, /* spike trend */
   15  Kabu_TRADE_MARKET_TYPE_B, /* random trend */
   16  Kabu_TRADE_MARKET_TYPE_C, /* falling trend */
   

   32  static f32 next_trade_market_typeA[TRADE_MARKET_ODDS_NUM] = {
   33    0.5f, /* Type A (50%) */
   34    0.3f  /* Type B (30%) */
   ⋮
   46    0.3f  /* Type B (30%) */
   ⋮
   59  for (i = 0; i < TRADE_MARKET_ODDS_NUM; i++) {
   60    if (chosen < *next_type_market) {
   61      break;
   ⋮
   64    chosen -= *next_type_market;
   ⋮
   69    i = 0;
   

   Checked against the evidence by its author, an AI model, 2026-10-22.

   Checked by a second AI model, 2026-10-22.

   In the claim ledger

4. ^In the USA GameCube release (GAFE01_00, ACreTeam/ac-decomp), a type B week (Kabu_decide_price_schedule_typeB) walks from the Sunday price through Monday to Saturday. Each day an fqrand draw below the drop chance (10% at first) multiplies the price by 0.7, caps it at 0.8 × the Sunday price (the code's min_price, which works as a ceiling here), and multiplies the drop chance by 0.3, capped at 10%. Any other day multiplies the price by a factor that starts at 1.05 and grows by 0.01 after each rise, and adds 0.14 to the drop chance. Each day's price is stored as a whole number; the walk keeps the fraction.CodeACreTeam/ac-decomp
   How we know

   102#define TRADE_MARKET_B_SUNDAY_PRICE_MULT 0.8f /* 0.8x (80%) minimum possible price */
   ⋮
   123    if (fqrand() < price_decrease_percent) {
   124      current_price *= TRADE_MARKET_B_PRICE_DECREASE_RATE; /* decrease price */
   125      if (current_price > min_price) {
   ⋮
   127          current_price = min_price;
   ⋮
   131      price_decrease_percent *= TRADE_MARKET_B_PRICE_DECREASE_LOWER_RATE;
   ⋮
   138      current_price *= current_price_mult;
   139      current_price_mult += TRADE_MARKET_B_PRICE_INCREASE_RATE;
   140      price_decrease_percent += TRADE_MARKET_B_PRICE_DECREASE_ODDS_RATE;
   ⋮
   143    *prices++ = current_price; /* move to next day save slot */
   

   Checked against the evidence by its author, an AI model, 2026-10-22.

   Checked by a second AI model, 2026-10-22.

   In the claim ledger

5. ^In the USA GameCube release (GAFE01_00, ACreTeam/ac-decomp), a type A week (Kabu_decide_price_schedule_typeA) first builds a type B week, then sets one day, Monday to Friday with equal odds (fqrand × 5, truncated, plus Monday), to 8 × the Sunday price: 560 to 1,040 bells (computed; 1,040 only from a 130-bell Sunday, see turnip-sunday-price).CodeACreTeam/ac-decomprevised
   How we know

   80#define TRADE_MARKET_A_SPIKE_DAYS 5
   81#define TRADE_MARKET_A_SPIKE_DAY_BEGIN lbRTC_MONDAY
   82#define TRADE_MARKET_A_SPIKE_MULTIPLIER 8.0f
   ⋮
   93  Kabu_decide_price_schedule_typeB(); /* start with a 'random' trend */
   ⋮
   97  spike_day = fqrand() * TRADE_MARKET_A_SPIKE_DAYS;
   98  spike_day += lbRTC_MONDAY;
   

   Checked against the evidence by its author, an AI model, 2026-10-22.

   Revised after a check by a second AI model, 2026-10-22.

   In the claim ledger

6. ^In the USA GameCube release (GAFE01_00, ACreTeam/ac-decomp), a type C week (Kabu_decide_price_schedule_typeC) multiplies the price each day from Monday to Saturday by 0.8 + 0.14999998 × r, with r from fqrand in [0, 1), so each day is 80% to 95% of the day before; a decompiler's comment says the constant stands for 0.15.CodeACreTeam/ac-decomp
   How we know

   147#define TRADE_MARKET_C_ADJUST_MULT_SPREAD 0.14999998f /* mwcc doesn't generate the same */ //0.15f
   148#define TRADE_MARKET_C_ADJUST_MULT_BASE 0.8f
   ⋮
   159    current_price *= (TRADE_MARKET_C_ADJUST_MULT_BASE + TRADE_MARKET_C_ADJUST_MULT_SPREAD * fqrand()); /* [80%, 95%) */
   

   Checked against the evidence by its author, an AI model, 2026-10-22.

   Checked by a second AI model, 2026-10-22.

   In the claim ledger

7. ^In the USA GameCube release (GAFE01_00, ACreTeam/ac-decomp), Kabu_manager runs at the start of play and whenever the clock's day of the month changes during play. On the date the week's table was set (a Sunday), it picks a new market type and new Monday-to-Saturday prices and keeps the Sunday price. On any other date it redraws the whole week, Sunday price included, only if the clock is at or past that Sunday 00:00 plus 7 days, or earlier than that Sunday minus 7 days; the new table is dated the Sunday at or before the clock's date. So a clock moved to any date from the Sunday 7 days before the table's Sunday through the Saturday after it keeps the whole table, except the table's Sunday itself, which keeps only the Sunday price.CodeACreTeam/ac-decomprevised
   How we know

   222  if (lbRTC_IsEqualDate(
   ⋮
   227    Kabu_decide_price_schedule_without_sunday(); /* reset non-sunday prices & the trend type */
   ⋮
   234    lbRTC_Add_DD(&week_ahead, lbRTC_WEEK);
   ⋮
   237    lbRTC_Sub_DD(&week_behind, lbRTC_WEEK);
   ⋮
   239    if (lbRTC_IsOverTime(&week_ahead, Common_GetPointer(time.rtc_time)) == lbRTC_OVER ||
   240        lbRTC_IsOverTime(&week_behind, Common_GetPointer(time.rtc_time)) == lbRTC_LESS
   

   19  kabu_update_time->hour = 0;
   ⋮
   24  lbRTC_Sub_DD(kabu_update_time, kabu_update_time->weekday);
   

   188  Kabu_decide_trade_market();
   189  Kabu_decide_price_without_sunday();
   190  Kabu_set_schedule_day();
   

   421  if (t1->year < t0->year) {
   422    return lbRTC_LESS;
   ⋮
   435                      return lbRTC_LESS;
   ⋮
   439                  return lbRTC_LESS;
   ⋮
   443              return lbRTC_LESS;
   ⋮
   447          return lbRTC_LESS;
   ⋮
   451      return lbRTC_LESS;
   ⋮
   455  return lbRTC_OVER;
   

   509  if (Common_Get(time.rtc_time.day) != day) {
   510    Kabu_manager();
   

   535extern void mSDI_StartInitAfter(GAME* game, int renew_mode, int malloc_flag) {
   ⋮
   556    Kabu_manager();
   

   Checked against the evidence by its author, an AI model, 2026-10-22.

   Revised after a check by a second AI model, 2026-10-22.

   In the claim ledger