Knowledge Atlas

Learning Vault

A curated collection of industry-standard resources, techniques, and toolsets for the modern artist.

color

10 Godly Coloring Techniques (Digital Art) — Ross Draws

A compact set of practical coloring tips and painterly shortcuts aimed at improving color decisions and polish in digital painting.

technique

Ambient Occlusion & Light Study for Painters

YouTube tutorial by Marco Bucci on how ambient occlusion and ambient light affect digital painting — foundational for adding form and depth.

technique

Ambient Occlusion Tutorial – How to Paint AO

YouTube video covering ambient occlusion techniques without 3D asset baking — great for 2D artists.

lighting reference

Anatomy of Shadows

Educational diagram labeling shadow types and light sources on a bust, including Ambient Occlusion, Terminator, Core Shadow, Reflective Light, Indirect Light, Cast Shadow, Antumbra, Umbra, and Penumbra.

animation / screenshot reference

Animation Screencaps

A vast archive of animated film & TV series screenshots and screen captures, useful for reference and studying animation poses, lighting, and composition.

animation reference

Animationscreencaps

Archive of animated film and TV show screen captures: very helpful for studying lighting, composition, character silhouettes, and motion.

procreate

Art With Flo – 14 Free Procreate Brushes + 1-Hour Tutorial

ArtwithFlo offers 14 high-quality free Procreate brushes with a fully narrated 1-hour video tutorial on how to use each one.

technique

Blending colors with one click? I Bet you didn’t know about this Trick

YouTube tutorial showing a trick for blending colors more efficiently in digital painting, going beyond the mixer brush.

youtube creator

Bluefley – YouTube Channel

Bluefley00’s YouTube channel: concept art, digital painting process, fantasy & sci-fi illustrations.

tutorials

Bobby Chiu (YouTube) — drawing demos & live figure sessions

Level: Intermediate (concept + figure practice). Interviews, drawing demos and free live figure-drawing sessions (life drawing streams). Great for observational practice and industry advice from a professional concept artist/educator.

anatomy

Body Part Compilation – Warm Ups

Compilation tutorial of body part sketches and warm-up exercises for anatomy practice.

brushpack

Brush Pack – Emily Xu

A Gumroad brush set by Emily Xu, suitable for painterly rendering and stylized digital illustration.

brushpack

Brush Pack – Mateusz Urbanowicz

A Gumroad brush pack by Mateusz Urbanowicz, designed for watercolor-style digital painting and illustration.

brushpack

Brush Pack – Yuming Li

Gumroad brush pack by Yuming Li — ideal for illustrative & digital art workflows.

art / illustration live stream

CeltisArt – Twitch Channel

Freelance illustrator streaming live art, described as a ‘sweaty frog lady who likes spaghetti’.

character design

Character Design Live Stream Part 1

Aaron Blaise live-streamed character design session — sketch-to-idea process, anatomy decisions, and design critique from a professional animation artist.

character design

Character Design References – Visual Library

Organized visual reference library with character turnarounds, creature poses, environments, and more for concept artists.

character design

Character Rendering Process

Step-by-step character rendering progression showing Sketch, Shadow, AO (Ambient Occlusion), AO + Shadow, AO + Shadow + Color, and Final stages for a stylized female character.

character design

CharacterDesigns.com

A huge reference gallery of character design drawings, models, turnarounds, and stylized art for inspiration.

character design

CharacterDesigns.com (Home Section)

Main home page for CharacterDesigns.com – huge resource for character sheets, turnarounds, concept art, and model references.

art / illustration live stream

ChrissaBug – Twitch Channel

Independent artist & author streaming drawing and painting, with lots of chatting and cat fostering.

tutorials

Circle Line Art School (YouTube + website)

Level: Beginner → intermediate (perspective & environments). Huge collection of free step-by-step perspective and background drawing tutorials (one-point, two-point, cityscapes, architectural forms). The channel and website host hundreds of free lessons you can follow in the browser.

illustration

Clip Studio Paint

A professional illustration, comics, and 2D animation software widely used for comics and concept art. It supports raster and vector layers, has stabilization for inking, and a rich assets store.

color palette

Color Hunt

Free and curated color palettes, perfect for getting color inspiration or building a palette for your digital artwork.

color palette

Colorbox.io

Colorbox is a curated collection of color palettes and combinations ideal for digital design and illustration.

composition

Composition Studies – Tutorial

Old composition studies showing how to arrange elements effectively in artwork.

brushpack

Concept Art Empire – Photoshop Brushes

Collection of curated free and paid Photoshop brush packs specifically recommended for concept artists and digital painters.

color palette

Coolors

Color palette generator and inspiration tool. Create and explore harmonized color schemes easily.

color

Coolorus

Advanced color wheel application (addon) to choose and control color harmonies easily; useful for digital painters and illustrators.

course

Crafted by Robert – 2-Minute Building Drawing Challenge

Level: Intermediate (foundation strengthening). Free challenge-based drawing practice that pushes you to draw buildings from basic forms under time pressure — great for perspective & structural drawing.

course

Crafted by Robert – Contour & Blind Contour Drawing Guide

Level: Beginner. Free guide (with live-demo drawings) to master contour & blind-contour drawing — great for observational skills and hand-eye coordination.

course

Crafted by Robert – Negative Space Drawing Guide

Level: Beginner → intermediate. Free tutorial on negative space drawing — a subtle but powerful exercise to improve accuracy, composition and observational drawing.

resource list / course

CSP Master List – Carrd

Comprehensive list of free and paid Clip Studio Paint (CSP) resources, brushes, tutorials, and courses curated by the community.

course

Ctrl+Paint — Free Video Library

Level: Beginner → digital drawing. Hundreds of short free video lessons on digital painting + traditional drawing basics (contour, shading, value, composition). Great for bridging into digital art.

marketplace

Cubebrush Marketplace

A marketplace for digital art resources: tutorials, 3D models, textures, brushes, and more, created by professional artists.

youtube educator

Dave Greco – YouTube Channel

Dave Greco’s channel: sketching, character design, concept art, and practical drawing demos for digital artists.

software

David Revoy’s Free Krita Brush Bundle (2023)

David Revoy’s official Krita brush pack (38 brushes) explained in a blog + video. Great for digital painters using Krita.

concept

Design Cinema - Sketching 101 (FZD School / Feng Zhu)

Feng Zhu's Design Cinema episode on sketching fundamentals for concept art — gestures, silhouettes, and early-stage design considerations.

composition technique

Design Theory: Composition

YouTube tutorial titled 'Design Theory: Composition' that explores how to arrange elements in digital art or illustration to create strong visual flow, focus, and hierarchy.

digital painting technique

Digital Art Tutorial – Unknown Title (YouTube)

A digital art tutorial on YouTube (ID: iPM7vIbfdBc). Useful for workflow or digital painting techniques.

digital art technique

Digital Art Tutorial – Unknown Title (YouTube)

YouTube tutorial (ID: ucx8c52YMzU). Covers digital art techniques and workflow tips.

brushpack

Digital Oil Brushes for Photoshop – Martina Palazzese

Free downloadable oil-painting brush set for Photoshop created by Martina Palazzese. Excellent for digital painters wanting painterly texture.

painting

Digital Oils Photoshop Brush Pack – Free Download

Visual Arts Passage’s page for Jon Neimeister’s free digital oils brush pack, which simulates oil paint realism in Photoshop.

concept art

Digital Painting Brush Pack

Visual Arts Passage offers a free, powerful and versatile brush kit by Jon Neimeister for concept and digital painting.

fundamentals

Digital Painting Fundamentals: Basic Navigation

Ctrl+Paint's short lesson on the basics of navigating painting software — a foundational must-watch for beginners to digital painting tools and workflow.

workflow

Digital Painting in 5 EASY STEPS! - Tutorial

A friendly step-by-step rundown of a full digital painting workflow — from thumbnails to final pass — aimed at beginners and intermediate artists.

submission guideline / design standards

Dota 2 Workshop – Character Art Guide

Official FAQ page from Steam Support giving guidelines for submitting character art to the Dota 2 Workshop — covers requirements, format, tools, and quality standards.

tutorials

Draw with Jazza (Jazza) — YouTube

Level: Beginner → intermediate (character & stylized art). Energetic, practical tutorials and exercises for character design, digital & traditional drawing fundamentals, and fun practice projects. Many free, digestible lessons and challenges on YouTube.

course

Drawabox

Level: Beginner → intermediate. Structured, exercise-based drawing course focusing on fundamentals (line work, form, 3D space, perspective). Completely free; optional paid critique only if you want feedback.

anatomy

Drawing Arms – Tutorial

Step-by-step tutorial on how to draw arms with proper anatomy and proportions.

anatomy

Drawing Ears – Tutorial

Step-by-step tutorial on how to draw ears with proper anatomy and proportions.

anatomy

Drawing Eyes – Tutorial

Step-by-step tutorial on how to draw eyes with expression and accuracy.

anatomy

Drawing Feet – Tutorial

Explains how to draw feet with correct anatomy and perspective.

anatomy / details

Drawing Hair – Tutorial

Explains how to draw hair with flow, volume, and texture.

anatomy

Drawing Hands – Tutorial

Step-by-step explanation on how to draw hands with proper proportions and gestures.

anatomy

Drawing Head – Tutorial

Explains how to draw heads with correct proportions and facial structure.

course

Drawing Hub by Crafted by Robert – Free Tutorials & Exercises

Level: Beginner → intermediate. Collection of free drawing tutorials covering fundamentals: contour drawing, negative space, proportion, shading, perspective, with exercises and demo projects.

anatomy

Drawing Legs – Tutorial

Explains how to draw legs with correct anatomy and dynamic poses.

anatomy

Drawing Mouth – Tutorial

Explains how to draw mouths with proper anatomy and expressions.

anatomy

Drawing Neck – Tutorial

Explains how to draw necks with proper anatomy and proportions.

anatomy

Drawing Nose – Tutorial

Step-by-step tutorial on how to draw noses with proper anatomy and perspective.

anatomy

Drawing Torso – Tutorial

Tutorial explaining torso anatomy and proportions for character drawing.

art / illustration live stream

DZIKAWA – Twitch Channel

A digital & traditional artist streaming illustrations and sometimes manga. Streams every day except Mondays and Fridays.

stylized proportions

Elongated Character Silhouette

Very long, narrow character silhouette. The proportions are stylized — the torso is long, and limbs are quite slim. Could benefit from understanding real anatomical ratios before stylizing.

sketching / whiteboard

Excalidraw

Open-source online whiteboard with a hand-drawn feel, great for sketching, brainstorming, and diagramming visually.

lighting / form reference

Female Head, Light Reference Tool – William Nguyen

3D faceted female head model by William Nguyen on ArtStation — used as a lighting and form reference tool to study how light wraps around the head’s planes and features.

painting

Free Brush Pack: Digital Oils

Jon Neimeister’s free digital oils brush pack that simulates realistic oil painting stroke dynamics.

concept art

Free Brush Pack: Digital Painting Essentials

A versatile free brush pack by concept artist Jon Neimeister, containing textured, painterly and basic brushes for digital painting.

course

Free Drawing Course for Beginners — Skillademia

Level: Absolute Beginner. Free ~2-hour course teaching drawing materials, basic sketching and simple exercises — a gentle start if you never drawn before.

course

Free Online Drawing Course for Beginners — Dream & Draw Art School

Level: Beginner → basic stylized drawing. Series of free lessons: pencil/liner practice, basic sketching, watercolor sketching — good for traditional + creative start.

character illustration

Free Photoshop Brush Pack for Digital Character Painting

Domestika offers a free PSD brush pack by Georgi Georgiev, featuring brushes for skin texture, smoke, smudges, and magical effects.

brushpack

Free Photoshop Brushes – CreativeBloq

A curated collection of free Photoshop brushes offered by CreativeBloq for artists and designers.

brushpack

HABOOK Brush Pack

A Gumroad brush pack by HABOOK featuring expressive texture brushes for stylized digital illustration.

anatomy

How to Draw the Head from Any Angle

Proko's step-by-step approach for constructing the head so you can draw it from any viewpoint. Classic lesson for artists working on portraits and character heads.

style / color technique

HOW TO HYPERPOP! (draw with saturated colors)

YouTube tutorial on drawing in a hyper‑pop style, focusing on saturated colors and bold design.

feature study

How to Improve an Eye (Iterative Drawing in Action) — Sycra

Sycra’s step-by-step breakdown showing how multiple iterations can refine a single feature — great for focused practice on eyes and facial features.

lighting / shading technique

How to Paint Ambient Occlusion for Digital Painting – Blog Tutorial

Blog post tutorial explaining how to apply ambient occlusion in digital paintings step by step.

hair

How To Paint Hair - Digital Painting Tutorial

Ross Tran (RossDraws) walks through his approach to painting hair digitally — from base shapes to highlights — with practical, easy-to-follow steps.

skin

How To Paint Skin - Digital Painting Tutorial!

RossDraws' extended tutorial and demo on painting realistic skin digitally, covering color selection, layering, and finishing touches.

artist mindset

How To Stop Procrastinating: Lessons from Pro Artist

YouTube video discussing how professional artists deal with procrastination and negative loops in their creative workflow.

icons / ui

Iconify Icon Sets

Huge collection of icon sets available via Iconify — useful for UI designers and illustrators needing scalable icons.

course

Introduction to the Science of Drawing — Alison

Level: Beginner / theoretical + practical. Free course covering basic sketching concepts, history and theory of drawing as art form — helpful to build conceptual understanding.

mindset

It’s Not The Brushes: It’s You. A Discussion on Digital Brush Choice

A article about how improving your art is more about skill than having expensive brush packs; helps perspective on brush addiction.

tutorials

James Gurney (YouTube)

Level: Intermediate → advanced (painting + observational drawing). Master painter/illustrator (Dinotopia) sharing plein-air, sketchbook, perspective and color/painting demos. Excellent for artists who want to deepen observational drawing, color, and painting knowledge (free videos on YouTube).

brushpack

Jingsketch Brushes

A highly popular Jingsketch brush set widely used for digital illustration, painting, and character art.

art / illustration live stream

Kloirr – Twitch Channel

A freelance illustrator from Seattle who loves painting landscapes and sometimes plays video games.

software

Krita – Free Digital Painting and Animation Software

Krita is a powerful free and open-source raster graphics application designed for artists, concept painters and animation.

pose reference / figure drawing

Line-of-Action

Online tool for timed figure-drawing practice (gesture, anatomy, animals, hands) with a customizable timer and many reference photos. Great for improving gesture drawing.

color palette

Lospec Palette List

Curated list of palettes for pixel art and digital design; great for stylized or retro art projects.

posing / figure reference

MagicPoser Web App

Browser-based 3D posing tool where you can set up character models and poses to use as reference for figure drawing.

tutorials

Mark Crilley (YouTube)

Level: Absolute beginner → intermediate (manga, characters). Step-by-step narrated 'How to Draw' tutorials (faces, manga, perspective, hair, chibis). Very beginner-friendly; great for rapid practical exercises and learning a variety of character styles.

coloring techniques

Marker Coloring Techniques for Trees

A reference sheet showing how to color trees using alcohol markers. It demonstrates how to create three values with a single marker and compares different marker brands and color choices.

drawing fundamentals / workflow

Mini tutorial: From Basics to Complexity

A more compact tutorial showing the artist’s workflow — using simple shapes and gradual building to draw complex parts (example: hands), emphasizing fundamentals over imitation. ([deviantart.com])

youtube educator

ModernDayJames – YouTube Channel

James’ channel covers anatomy, perspective, design, form, and foundational drawing techniques. Known for very structured, easy-to-follow lessons.

figure drawing / pose & movement

Nsio Explains: Advanced Dynamism

An advanced tutorial building on basic dynamism — focuses on more complex pose dynamics, weight distribution, balance, and natural motion. ([deviantart.com])

drawing fundamentals / workflow

Nsio Explains: Constructing and Analysing

Tutorial on construction, self-analysis and checking proportions/structure before refining — helps avoid compounding mistakes early in the drawing process.

drawing fundamentals / perspective

Nsio Explains: Distortion in Perspective

A deeper dive into perspective — explains common mistakes and how to avoid distortion when constructing perspective drawings.

figure drawing / pose & movement

Nsio Explains: Dynamism

Tutorial about adding dynamic flow and life into poses — using primary and secondary line of action to improve character drawings.

figure drawing / head & face

Nsio Explains: Facial Proportions

Guide to facial proportions and head construction — helpful when drawing faces with consistent proportions and stylized proportions.

drawing fundamentals / foreshortening

Nsio Explains: Foreshortening

An in-depth explanation of foreshortening and how to draw limbs or objects coming toward the viewer — tutorial #8 in the “Nsio Explains” series.

drawing fundamentals / structural guides

Nsio Explains: Introduction to Guidelines

An introductory tutorial about using construction guidelines (cubes, cylinders, planes) to simplify complex forms — helpful for beginners.

drawing fundamentals / figure drawing

Nsio Explains: Learning Order to Human Drawing

A guide outlining the recommended learning order and foundations for human figure drawing — what to practice first, and why.

drawing fundamentals / line work

Nsio Explains: Line Dynamics

An essential guide about the nature of lines — how to draw expressive, dynamic lines rather than relying on static outlines. Covers stroke weight, flow, and how lines convey mood and movement. ([deviantart.com])

drawing fundamentals / perspective

Nsio Explains: Perspective

Tutorial on 3-point perspective, vanishing points, eye-level and how to properly render three-dimensional forms — part of Nsio’s fundamental drawing series.

art mindset / theory

Nsio Explains: Psychological take on making art

A conceptual tutorial discussing the mindset, motivation and mental approach to art creation and improvement.

drawing fundamentals / lighting & shading

Nsio Explains: Shading Basics

A straightforward shading tutorial — explains how understanding 3D and surface orientation makes believable shading almost automatic.

drawing fundamentals / shape simplification

Nsio Explains: Simplifying the Complexity

Shows how to break complex human forms into basic shapes (cubes, cylinders, spheres) for easier drawing and understanding of structure. Helps with form simplification. ([deviantart.com])

drawing fundamentals / 3d form

Nsio Explains: Understanding 3D

Explores how to think in 3D space to improve form, perspective and overall drawing realism — part of Nsio’s foundational series.

figure drawing / proportions

Nsio Explains: Understanding Proportions

Tutorial focusing on human figure proportions — how to place and measure body parts reliably before adding detail.

brushpack

Paint Stroke Brushes – ResourceBoy

A downloadable set of Photoshop paint-stroke brushes provided by ResourceBoy, ideal for texture and stylized effects.

facial anatomy

Painting Parts of the Face

Comprehensive infographic for realistic facial feature rendering covering eyes, nose, ears, and mouth with step-by-step painting instructions and lighting techniques.

color

Painting Skin Tones and How Light Affects Color

Marco Bucci demonstrates practical methods for painting flesh — how lighting changes skin color and quick techniques to simplify the process.

color palette

Palitra — Color Palettes

Simple app for browsing, saving, and exporting color palettes. Handy for when working on illustrations and digital paintings.

tool / plugin

Perspective Tools V2 for Photoshop – Sergey Kritskiy

Photoshop extension panel that allows you to create perspective & parallel grids, warp layers to perspective, and unwrap distorted layers—useful for concept artists and digital painters.

photo reference / stock

Pexels

Free stock photo and video resource, useful for reference, textures, backgrounds, or concept inspiration.

figure drawing / anatomy

Posemaniacs

A reference site offering 3D models of hands, bodies and dynamic poses to help artists train gesture drawing and anatomy.

posing / reference

PoseMy.Art

Web-based 3D posing tool for figure reference — adjust joints, body type, and lighting to create custom poses for drawing reference.

clothing / folds

Practice with Clothing Folds – Tutorial

Step-by-step tutorial on how to draw and understand clothing folds in character art.

anatomy

Proko - How to Draw Eyes (Structure and Detail)

Proko's in-depth breakdown of eye anatomy, structure, and drawing technique — excellent for portrait and character artists.

youtube educator

Proko – YouTube Channel

Proko’s channel for learning figure drawing, anatomy, caricature, and gesture drawing in an accessible but in-depth way.

reference / image viewer

PureRef – Lightweight Reference Image Viewer

Lightweight reference image viewer (tile, arrange, zoom). Artists on Reddit often use it for moodboards/reference boards. Free (donation optional).

posing / figure reference

Quickposes

Quickposes is a tool for art students, illustrators or anyone who wants to focus on improving their drawing skills. By practicing gesture drawing you will not only get better at recognizing certain aspects of poses, but you will also build a visual library of characters and models.

figure reference

Reference Angle

Tool to generate reference photos of a human body at multiple angles to help with figure drawing and anatomy studies.

tutorials

Scott Robertson (YouTube) — perspective & design tutorials

Level: Intermediate → advanced (technical perspective). Industrial-design / perspective-focused tutorials and lectures (very strong for technical perspective, vehicle and form construction). Free videos and lecture clips on YouTube.

art fundamentals

Shading Fundamentals for Trees

A reference sheet explaining shading fundamentals using spheres and tree canopies, covering highlights, light, midtone, core shadow, and reflected light. It also shows how to break a tree into shadow groups.

lighting / form reference

Shading Reference

A site that provides live models in many lighting setups for shading practice — useful for value studies and light-form understanding.

figure reference

Shading Technique Comparison

Illustration contrasting incorrect (detail-first) vs. correct (shadow-first) shading approaches for 3D figures, demonstrating proper light modeling on human anatomy.

art prompt / challenge

Silent Manga Challenge – X (formerly Twitter) Post

Post from Silent Manga Challenge community on X (formerly Twitter) — contains reference/competition art prompts useful for manga & sequential art practice.

color

Simplifying Light and Color with Marco Bucci (Livestream demo)

Marco Bucci shows techniques to simplify color and light decisions to speed up and improve paintings, ideal for concept and illustration work.

youtube educator

Sinix Design – YouTube Channel

Sinix’s YouTube channel: tutorials on imaginative anatomy, design theory, stylized painting, and creative process + speedpaints.

posing / reference

SketchDaily / reference.sketchdaily.net

SketchDaily reference tool (timers, flip, grid) — classic resource used across sketching communities on Reddit.

brushpack

Starter Brush Pack 2023 – MB

A Cubebrush starter pack containing essential brushes for digital painting and concept art workflows.

drawing tutorial

Step-by-Step Drawing Guide

Hand-drawn instructional sheet covering texture techniques, form construction, shading methods, perspective systems, organic shapes, and anatomical proportions with German annotations.

drawing

Stream: Painting Live with Sarah

Live painting stream where Sarah covers sketching, color, and lighting in a 2-hour session.

youtube educator

Sycra – YouTube Channel

Sycra’s YouTube channel: deep dives into anatomy, character design, iterative drawing, critique, and artist development.

tutorials

The Virtual Instructor (YouTube + website)

Level: Beginner → intermediate (multi-medium). Many free video lessons covering pencil, charcoal, colored pencil, ink and basics of drawing. The website also hosts organized free lessons (no mandatory app).

nature / form / landscape

Tree Trunk and Branching Structure Reference

An illustration showing the anatomical structure of a large tree, focusing on the main trunk, primary and secondary branches, and the natural taper and rhythm of the wood. This is a common artistic reference for studying natural form, volume, and how light interacts with the cylindrical shapes of wood and bark.

illustration / vector reference

unDraw Illustrations

Collection of free, open-source illustrations that can be used in your projects or as conceptual reference.

photo reference / stock

Unsplash

Massive library of free high-resolution stock photos, usable as reference images in digital art.

typography / design asset

Usable Google Fonts (Figma File)

Figma document listing usable Google Fonts for design / typography workflows, useful for illustrators working with text elements.

color theory

Value and Hue Understanding Guide

A reference explaining how different hues have inherent value ranges and how saturation can affect perceived value. Includes examples with blues, yellows, and oranges, and how these affect scene readability.

photo reference / stock

ViShopper Cut-Out People

Large collection of cut-out people (transparent background) photos that are great as reference or for use in composition and backgrounds.

photo reference / stock

ViShopper Cut-Out People (Search)

Searchable collection of cut-out people photographs with transparent backgrounds — useful for layout, composition and reference design.

critique / feedback

What's Wrong With My Drawing?

A community critique site where artists can submit their drawings to get feedback, identify anatomical issues, proportions, and improve their work.

drawing fundamentals

Will Weston Drawing Lectures – Pinterest Board

Pinterest board collecting drawing lectures by Will Weston — good reference for traditional drawing fundamentals.

perspective / drawing aid

x6ud Perspective Sketch Tool

An interactive browser-based perspective drawing tool to help artists draw perspective grids easily.

course

ZEPHY – Anatomy Drawing Tutorials (Free Printable Sheets)

Level: Beginner → intermediate. Free downloadable anatomy drawing worksheets and muscle charts — useful for figure & anatomy studies.

course

ZEPHY – Free Beginner Drawing Course (3-Day Starter)

Level: Beginner. A simple 3-day drawing course focusing on fundamentals: lines, shapes, proportions, volumes, perspective. Includes cheat-sheets and exercise sheets. Starts free.