Level-Up

The last enemy falls, the spoils window counts out EXP and gold, and sometimes a second window announces that someone's level went up. Underneath, the game splits the EXP among the survivors, compares each one against a threshold curve, and grows eight stats per level crossed. The numbers are tidy: the whole XP curve is a closed form, and every stat's growth is a normalised curve that lands each character exactly on their level-99 ceiling. Fully ported

At a glance

Applier: FUN_801E9504 in the battle overlay (PROT 0898) - XP, stat growth and the level bump in one routine, called once per surviving party member.
Tables: Three static tables in SCUS_942.54: per-level XP deltas, three growth curves, and a per-character parameter block (addresses).
Record fields: Cumulative XP +0x004, stat window +0x11C..+0x12D, displayed level +0x130 in the 0x414-byte character record.
Parser / engine: legaia_asset::level_up_tables reads the tables from the user's executable at boot; engine-core::levelup::LevelUpTracker applies them.
Confidence: Confirmed - disassembly, byte-exact against a single-level capture.
Used by: Battle, Status screen, ROM patcher (starting level, EXP scale).

From victory to banner

1Victorythe end-of-action gate sees no living monsterbattle action SM 2SpoilsEXP summed x3/4, gold halved twice, drop rolls; XP split evenly among survivorsreward resolver 3Thresholdcumulative XP vs the scaled curve; loop while threshold <= XPapplier 4Growthper crossed level: HP max, MP max and six stats grow along the character's curve, with jitterapplier 5Recordcumulative XP, next threshold and level byte written - the three fields the Status menu drawssave record 6Banner"<name>'s level increased!" window above the spoils windowengine-ui

Two things surprise players: a level-up raises maximum HP and MP but does not heal you, and one big award can jump several levels at once. Dead party members get no XP.

XP curve

The per-level XP delta is ⌊n²/4⌋ + 1 (1, 2, 3, 5, 7, 10, …, 2402 over 98 levels); the base threshold for a level is the running sum of those deltas. The applier then scales that sum and, for Noa and Gala, corrects it.

Step	Rule
Base sum	`sum(level) = Σ delta[0..level]`
Scale, level < 17	`threshold = sum × 9,999,999 / 0x140FE` (about ×121.69)
Scale, level ≥ 17	`threshold = sum × 121`
Party-slot correction	Noa subtracts and Gala adds `threshold × 20 / divisor(level)`; the divisor curve runs 125, 251, 376, … so the correction shrinks from ~16% at L1 to ~0.5% mid-game.
Loop	`do { level++; grow stats } while (threshold ≤ XP)` - several levels per award are possible.

Worked example - the level-2 thresholds a New Game Status screen shows: Vahn and Terra 121, Noa 102, Gala 140. The base curve continues 365, 730, 1338, 2190, … 9,646,483 at level 99. The engine carries the closed-form curve in legaia_save::retail_xp_table() and re-reads the same values from the user's executable at boot, so the two cross-check each other.

Stat gains

Each level crossed grows eight stats - HP max, MP max and the six battle stats - from two tables: three growth curves (one byte per level, each ramp settling to a plateau) and a per-character block of eight {start, max, jitter, row} entries, one per stat.

Term	Rule
Core gain	`(max − start) × curve[row][level−1] / 0x24C0`
Jitter	`+ rand() % (2×jitter + 1) − jitter`, one BIOS `rand()` per stat per level
Floor and caps	`max(1, core + jitter)`; then HP ≤ 9999, MP ≤ 999, SP ≤ 280, others ≤ 999
Why `0x24C0`	Every curve sums to exactly 9408, so the gains accumulate to exactly `max − start` over 98 levels: each stat lands on its ceiling at level 99.

Worked example - Noa, L2 to L3, HP: (4500 − 150) × 82 / 9408 = 37, jitter ±4; the capture shows +39. Every one of her eight deltas that battle (MP +5, stats +2/+4/+4/+3/+4/+3) sits inside its core ± jitter band. Two per-character facts from the captures: Noa also gains +40 max Spirit per level, Gala gains none.

What a level-up writes

Offset Field Note

+0x004 Cumulative XP The value the threshold loop compares against; the Status menu draws it as Experience.

+0x11C..+0x12D Record-side stat window 9 u16: HP max, MP max, a constant 100 at +0x120, six stats. Grown first, then mirrored to the live window +0x104..+0x11B.

+0x120 Per-stat cap constant 100 Constant across every captured save; not Spirit max. The runtime 999 clamp is a code constant.

+0x130 Displayed level The byte the Status screen reads as LV and the "Level 99" cheat targets. Incremented once per level-up event, never re-derived from XP.

Offset	Field	Note
`+0x004`	Cumulative XP	The value the threshold loop compares against; the Status menu draws it as Experience.
`+0x11C..+0x12D`	Record-side stat window	9 u16: HP max, MP max, a constant 100 at `+0x120`, six stats. Grown first, then mirrored to the live window `+0x104..+0x11B`.
`+0x120`	Per-stat cap constant 100	Constant across every captured save; not Spirit max. The runtime 999 clamp is a code constant.
`+0x130`	Displayed level	The byte the Status screen reads as LV and the "Level 99" cheat targets. Incremented once per level-up event, never re-derived from XP.

A level-up is not a heal. The applier stores to eleven addresses and every one is a maximum, a stat or a level; current HP and MP appear nowhere in it, and its only call is the BIOS rand. The capture agrees: Noa enters her L2-to-L3 fight at 164/182 HP and settles at 164/221 - ceiling up, wound unchanged.

The port

World::apply_battle_xp splits the reward among survivors (integer divide) and calls LevelUpTracker::grant_xp per slot; multi-level jumps collapse into one LevelUpResult.
apply_to_record grows the record window, mirrors it live, and leaves current HP / MP alone. The port keeps its own level byte at +0x100 (always zero in retail) and hydrates the tracker from it on load.
Jitter is opt-in (with_level_up_jitter(seed), a faithful BIOS-rand LCG) so replay and determinism oracles stay bit-identical; it is off by default.
The banner (LevelUpBanner, 180 frames) and the spoils report are retail's two framed windows, drawn from geometry measured off a capture. Two known gaps: only the last character's banner is shown, and both windows draw over the returned field scene rather than over the battle.

How we know

Function / data	Address	What it proves	Dump
Level-up applier	`FUN_801E9504`	Threshold scaling, the do-while loop, the growth formula, the eleven stores (no current-HP write).	`overlay_battle_action_801e9504.txt`
Reward resolver	`FUN_8004E568`	Calls the applier once per surviving member after dividing the EXP pool.	`8004e568.txt`
XP delta table	`DAT_80076AF4`	98 u16 entries equal to `⌊n²/4⌋+1`; the applier's aliases are its only readers.	SCUS data
Correction divisor	`0x80070A2C + level × 0x28`	The head of the GTE sine table sampled at stride 0x28 - a look-alike of an XP table, but only ever used as the Noa / Gala divisor.	SCUS data
Growth curves	`DAT_800769CC`	3 rows, stride `0x62`, each summing to `0x24C0`.	SCUS data
Per-character block	`DAT_80076918`	Stride `0x3C`: 8 × `{u16 start, u16 max, u8 jitter, u8 row}` per Vahn / Noa / Gala; `start` matches the new-game template.	SCUS data
Single-level capture	Noa L2→L3 triplet	Byte-exact check of the growth formula; the three-phase write order (record, live copy, battle-end settle).	`crates/mednafen/tests/real_saves.rs`
Engine oracles	`crates/engine-core/tests/growth_curve_disc.rs`	Installed curve `start` values vs the new-game seed; Noa's L2→L3 core HP 37 / MP 6.	-

Capture footprints and look-alikes

Phase	Window	Writes
Record write	pre → mid₁	`+0x11C..+0x12D`, `+0x004`, `+0x130` (+1)
Live copy	mid₁ → mid₂	`+0x104..+0x11B` (HP max, MP max, six live stats)
Settle	mid₂ → post	`+0x106 / +0x10A / +0x10E` - the battle-end resync, not a refill

Multi-level captures (vahn_4_level_jump and siblings, codified in engine_core::levelup::observations) pin write regions but not per-level rates; the single-level Noa pair is the arithmetic oracle. A Fire Book I use writes one region, +0x185..+0x188: a count-prefixed list of displayed-skill ids read only by the menu's status renderer (CharacterRecord::displayed_skills). The Seru-struct +0x74 reads are the actor's colour word (FUN_800480D8 stamps 0x00808080), not a growth grant. The grant tables are not in PROT.DAT at all.

Battle-actor stat struct (runtime, distinct from the record)

DAT_801C9370[slot] points at the in-battle actor (8 slots: party 0..2, monsters 3..7). Party actors are initialised by FUN_80053cb8 from the record's live window, monsters by FUN_80054cb0 from the monster archive; both write the same layout. Stats are working / base pairs - the working copy takes buffs and damage, the +2 base copy serves un-buff and percentage math.

Offset Field

+0x14C / +0x14E HP current / max (party: live +0x106 / +0x104)

+0x150 / +0x152 MP current / max (party: live +0x10A / +0x108)

+0x154 / +0x156 AGL working / base

+0x158 / +0x15A ATK working / base

+0x15C / +0x15E UDF (physical defence) working / base, plus equip bonus

+0x160 / +0x162 LDF (magical defence) working / base, plus equip bonus

+0x164 / +0x166 SPD working / base, plus equip bonus

+0x168 / +0x16A INT working / base

+0x16C AI turn-eligibility gate (FUN_801E9FD4 skips the actor when 0)

+0x16E Side / element bit-field (record +0x12E; the charm hook ORs 0x380)

+0x170 Spirit gauge (party: live +0x10E; monster: constant 100)

+0x172 / +0x174 HP / MP battle-start snapshots

+0x176 Per-action transient, cleared on action-state entry

Offset	Field
`+0x14C / +0x14E`	HP current / max (party: live `+0x106 / +0x104`)
`+0x150 / +0x152`	MP current / max (party: live `+0x10A / +0x108`)
`+0x154 / +0x156`	AGL working / base
`+0x158 / +0x15A`	ATK working / base
`+0x15C / +0x15E`	UDF (physical defence) working / base, plus equip bonus
`+0x160 / +0x162`	LDF (magical defence) working / base, plus equip bonus
`+0x164 / +0x166`	SPD working / base, plus equip bonus
`+0x168 / +0x16A`	INT working / base
`+0x16C`	AI turn-eligibility gate (`FUN_801E9FD4` skips the actor when 0)
`+0x16E`	Side / element bit-field (record `+0x12E`; the charm hook ORs `0x380`)
`+0x170`	Spirit gauge (party: live `+0x10E`; monster: constant 100)
`+0x172 / +0x174`	HP / MP battle-start snapshots
`+0x176`	Per-action transient, cleared on action-state entry

Dumps: 80053cb8.txt, 80054cb0.txt, overlay_0898_801e9fd4.txt, overlay_0898_801e295c.txt.

Full write-up: docs/subsystems/level-up.md. Source: crates/engine-core/src/levelup.rs, crates/asset/src/level_up_tables.rs.

At a glance

From victory to banner

XP curve

Stat gains

What a level-up writes

The port

How we know

See also