That depends on what you mean by Renewal client. Ragnarok's Renewal upgrade was predominantly a change in game mechanics and an overhaul of the game content. This is for the most part independent of the client. My client could connect to a renewal-based server in its current state if I updated the networking protocol. The major differences between RagExe and RagExeRE were the introduction of the Lua interpreter and the overhaul of the user interface. I will be implementing neither of these, and probably nothing related to the 3rd classes.
As for customization, that is done by changing build parameters before compiling. You can think of it as a config file like Athena uses. Client patchers provide a dead simple way to customize the client, but most people are unaware of the staggering amount of work that goes into making a tool like NEMO. These customization patches have made out of necessity, and with source code available that necessity is gone.
Implementing skills is one of the biggest tasks in creating a client, simply because there are so many of them. Skills come in many different varieties, some requiring additional UI (e.g. warping, Graffiti), some need special character animations, some combine multiple effects, sounds, special damage and special hit effects. In addition to the player skills there are also many skills only used by monsters. At the moment I have about 14,000 lines of code just implementing the various visual effects, so it's easy to forget what's ready and what's not. Here's an overview of the current state of the 1st and 2-1 classes. ✓ means 100% done, ✗ means unimplemented or partially unimplemented. Most skills can be used just fine without implementing an effect, but for my 1st milestone I want to have at least 1-1, 2-1 and 2-2 skills fully implemented.
Swordman
✓ Bash
✓ Endure
✓ Increase HP Recovery
✓ Magnum Break
✓ Provoke
✓ Sword Mastery
✓ Two-Handed Sword Mastery
✓ Berserk
✓ Fatal Blow
✓ HP Recovery While Moving
Magician
✓ Cold Bolt
✓ Fire Ball
✓ Fire Bolt
✓ Fire Wall
✓ Frost Diver
✓ Increase SP Recovery
✓ Lightning Bolt
✓ Napalm Beat
✓ Safety Wall
✓ Sight
✓ Soul Strike
✓ Stone Curse
✓ Thunderstorm
✓ Energy Coat
Archer
✓ Arrow Shower
✓ Double Strafe
✓ Improve Concentration
✓ Owl's Eye
✓ Vulture's Eye
✓ Arrow Crafting
✓ Repel
Merchant
✓ Discount
✓ Enlarge Weight Limit
✓ Item Appraisal
✓ Mammonite
✓ Overcharge
✓ Pushcart
✗ Vending
✓ Cart Revolution
✓ Change Cart
✓ Crazy Uproar
Thief
✓ Detoxify
✓ Double Attack
✓ Envenom
✓ Hiding
✓ Improve Dodge
✓ Steal
✓ Back Slide
✓ Find Stone
✓ Sand Attack
✓ Stone Fling
Acolyte
✓ Angelus
✓ Aqua Benedicta
✗ Blessing
✓ Cure
✓ Decrease AGI
✓ Demon Bane
✓ Divine Protection
✓ Heal
✓ Increase AGI
✓ Pneuma
✓ Ruwach
✓ Signum Crusis
✗ Teleport
✗ Warp Portal
✓ Holy Light
Knight
✓ Bowling Bash
✓ Brandish Spear
✓ Cavalier Mastery
✓ Counter Attack
✓ Peco Peco Ride
✓ Pierce
✓ Spear Boomerang
✓ Spear Mastery
✓ Spear Stab
✓ Twohand Quicken
Wizard
✗ Earth Spike
✗ Fire Pillar
✓ Frost Nova
✗ Heaven's Drive
✗ Ice Wall
✓ Jupitel Thunder
✓ Lord of Vermillion
✓ Meteor Storm
✓ Quagmire
✗ Sense
✗ Sightrasher
✗ Storm Gust
✗ Water Ball
Hunter
✓ Ankle Snare
✓ Beast Bane
✓ Blast Mine
✓ Blitz Beat
✓ Claymore Trap
✓ Detect
✓ Falconry Mastery
✗ Flasher
✓ Freezing Trap
✓ Land Mine
? Remove Trap
✓ Sandman
? Shockwave Trap
✓ Skid Trap
? Spring Trap
✓ Steel Crow
✗ Talkie Box
Blacksmith (Note: Forging items not implemented!)
✓ Adrenaline Rush
✓ Hammer Fall
✓ Hilt Binding
✓ Power Maximize
✓ Power-Thrust
✓ Skin Tempering
✓ Weapon Perfection
✓ Enchantedstone Craft
✓ Iron Tempering
✓ Ore Discovery
✓ Oridecon Research
✓ Smith Axe
✓ Smith Dagger
✓ Smith Knucklebrace
✓ Smith Mace
✓ Smith Spear
✓ Smith Sword
✓ Smith Two-handed Sword
✓ Steel Tempering
✓ Weapon Repair
✓ Weaponry Reasearch
Assassin
✓ Cloaking
✓ Enchant Poison
✓ Grimtooth
✓ Katar Mastery
✓ Righthand Mastery
✓ Lefthand Mastery
? Poison React
✗ Sonic Blow
✗ Venom Dust
? Venom Splasher
Priest
✗ Aspersio
? B.S Sacramenti
✓ Gloria
✓ Impositio Manus
✓ Increase SP Recovery
✗ Kyrie Eleison
✓ Lex Aeterna
✗ Lex Divina
✓ Mace Mastery
✓ Magnificat
✗ Magnus Exorcismus
? Resurrection
✓ Safety Wall
✗ Sanctuary
✓ Slow Poison
✓ Status Recovery
✓ Suffragium
✗ Turn Undead
Bonus pictures:
Pet capture
Rental cart
Arrow crafting
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