Progression Overhaul (Phase 1)

• Completely redesigned progression economy — PSI, Pearls, Drift, and Void Cores
• 155-node PSI Grid with 8 upgrade branches
• 129-node Pearl Grid with permanent upgrades that survive ascension
• 76-node Drift Shop across 4 categories (Workshop, Reliquary, Submarine, Depths)
• Ascension requires 50% PSI Grid completion + PSI threshold
• Void Tree redesigned as endgame permanence system with OMEGA ending
• 30 Void Nexus nodes across 5 branches
• BUY ALL and AUTO-BUY toggles on all upgrade grids
• Infinite capstone upgrades on every tree branch
• Upgrade pinning to track specific nodes

Deep Dive & Arsenal (Phase 2)

• Deep Dive endless mode — replaces O2 with a pressure meter that builds over time
• Deep Dive milestone rewards at 100m, 200m, 300m, 400m, 500m
• 4 exclusive Deep Dive artifacts earned from milestones
• Emergency O2 reserve mechanic — extra seconds when your tank hits zero
• Shield system — absorbs boss hits, counter-pulse damages bosses on block
• 5 arsenal abilities: Torpedo (homing projectile), Concussion Blast (AoE stun), Mine Drop (proximity mines), EMP Burst (freeze all fish), Beam (sweeping laser)
• Boss stat requirement gates — visible DPS, O2, pressure, and shield checks on milestone bosses

The Trench — Zone 6 (Phase 3)

• New zone: The Trench — the deepest abyss with no O2, only crushing pressure
• 3 unique Trench fish: Blink Stalker (teleports on hit), Fission Eel (splits into copies), Void Phantom (invisible until close)
• 2 Deep Dive exclusive fish: Phase Drifter and Split Shade
• Trench Horror boss with pressure waves, void zones, and homing orbs
• 6 Trench-exclusive artifacts forgeable from Trench Salvage
• Zone 6 shop with unique upgrades and Trench currency

UI Overhaul (Phase 4)

• Consolidated 13 tabs into 4 main tabs with sub-tabs
• Horizontal tab bar with animated transitions
• Dive controls redesigned — zone preview with sub and fish, info panel below
• Notification dot system — tabs glow when you can afford upgrades or have new content
• 20 submarine skins and 16 cursor designs in Cosmetics
• Full settings panel: audio sliders, display modes, UI scale, graphics toggles
• Interactive tutorial for new players
• Comprehensive How to Play guide

Performance & Dive HUD (Phase 5)

• Unified dive HUD panel system — PSI counter, combo display, depth meter, ability bar
• Circular O2/Pressure gauge with brass needle, zone-colored arcs, and tick marks
• Ability cooldown bars on the ability button bar
• Zone shop integration with per-zone currencies
• Ability SFX — unique procedural sounds for all 5 abilities
• Forge confirmation modal for expensive operations

UI Consolidation (Phase 6)

• Merged Artifacts & Forge into a single unified tab
• Each artifact card shows three states: owned (upgrade), forgeable (forge button + cost), or undiscovered
• Forgeable artifacts from locked zones hidden to prevent spoilers
• HUD-style Artifacts header with salvage counter, stats, and pity progress
• Redesigned Progress tab with 3-column milestone grid and stat cards
• Upgrade grids vertically centered, sub-tabs centered
• Zone Mastery scrolls with upgrades instead of stealing viewport space

Fish AI Overhaul (Phase 6)

• Minnows flock in schools — scatter when cursor approaches, reform after
• Fish flee from nearby deaths — visible chain reactions with AoE
• Sharks chase your sub with speed bursts
• Puffers inflate on cursor proximity, push nearby minnows away
• Jellies pulse rhythmically — burst forward, drift, repeat
• Eels lurk still, strike fast when you pass, then retreat
• 4 depth tiers adjust spawn rates — tougher fish deeper
• Minimum fish count of 50 so later zones stay populated

Keybind Remapping (Phase 6)

• Rebind all 6 actions in Settings (Torpedo, Concussion, Mine, EMP, Beam, Surface)
• Click to rebind — collision detection auto-swaps conflicting keys
• Modifier keys blocked from binding
• Ability bar dynamically shows custom keybinds
• All settings persist across sessions

Combat Depth (Phase 6)

• Boss phase transitions — 0.5s invulnerability at 60% and 30% HP with particle burst
• Attack telegraph — red arc fills before boss attacks for dodge window
• Torpedo smoke trails, concussion double-ring distortion, EMP electric arcs, beam burn particles
• Depth atmosphere — vignette tightens with depth, progressive water darkening

25-Boss System

• 25 milestone bosses across 5 zones at depths 20m, 50m, 90m, 130m, 180m
• 5 unique zone final bosses with custom abilities
• Trench Horror as the ultimate Zone 6 boss
• Boss trophy wall in Bestiary with progressive reveal
• Bestiary with CREATURES, BOSSES, and MILESTONES tabs — 7 kill tiers per species

Artifacts & Forge

• 45 artifacts: 6 per zone + 5 global + 4 Deep Dive exclusive
• Forge system — craft artifacts from salvage, upgrade to Lv.10 for 5x effect
• Pity system guarantees drops after 200 kills or 30 treasure
• Rarity tiers: Common, Rare, Epic, Legendary

Steam Integration

• 100 Steam achievements across 12 categories
• Achievement popup notifications in-game
• Window mode support: Windowed, Fullscreen, Borderless (F11 toggle)

Audio

• 19 procedural SFX generated via Web Audio API
• Ambient underwater drone with depth-reactive frequency
• Native audio playback through Godot
• Separate Master, Music, and SFX volume controls

Polish & Performance

• Larger O2 gauge for better readability
• Restyled speech bubbles with HUD panel styling
• Power-up orbs can't overlap bottom HUD
• Per-frame performance optimizations in game loop
• 3 save slots with auto-save
• Offline PSI earning while away