Css Fundamentals

CSS Fundamentals Skill

Master core CSS concepts: selectors, specificity, box model, positioning, and units.

Overview

This skill provides atomic, focused guidance on CSS fundamentals with type-safe parameters and comprehensive validation.

Skill Metadata

Usage

Skill("css-fundamentals")

Parameter Schema

parameters:
  topic:
    type: string
    required: true
    enum: [selectors, specificity, box-model, positioning, units, display]
    description: The CSS fundamental topic to explore

  level:
    type: string
    required: false
    default: beginner
    enum: [beginner, intermediate, advanced]
    description: Depth of explanation

  include_examples:
    type: boolean
    required: false
    default: true
    description: Include code examples

validation:
  - rule: topic_required
    message: "Topic parameter is required"
  - rule: valid_enum
    message: "Topic must be one of: selectors, specificity, box-model, positioning, units, display"

Topics Covered

Selectors

• Element, class, ID selectors
• Attribute selectors [attr], [attr=value]
• Pseudo-classes :hover, :focus, :nth-child()
• Pseudo-elements ::before, ::after
• Combinator selectors >, +, ~

Specificity

• Specificity calculation (0,0,0,0)
• Cascade order rules
• !important usage and pitfalls
• Inheritance patterns

Box Model

• Content, padding, border, margin
• box-sizing: border-box vs content-box
• Margin collapse behavior
• Inline vs block dimensions

Positioning

• static, relative, absolute, fixed, sticky
• Stacking context and z-index
• Containing block rules
• Offset properties (top, right, bottom, left)

Units

• Absolute: px, pt, cm
• Relative: em, rem, %, vh, vw
• Newer units: ch, lh, cqi, cqw
• When to use which unit

Retry Logic

retry_config:
  max_attempts: 3
  backoff_type: exponential
  initial_delay_ms: 1000
  max_delay_ms: 10000
  retryable_errors:
    - TIMEOUT
    - RATE_LIMIT
    - TEMPORARY_FAILURE

Logging & Observability

logging:
  entry_point: skill_invoked
  exit_point: skill_completed
  log_parameters: true
  log_response_size: true
  metrics:
    - invocation_count
    - success_rate
    - avg_response_time

Quick Reference

Specificity Calculator

Inline styles    → 1,0,0,0
ID selectors     → 0,1,0,0
Classes/attrs    → 0,0,1,0
Elements         → 0,0,0,1

Example: div#header .nav a:hover
         0,1,2,2 (ID=1, class+pseudo=2, elements=2)

Box Model Visual

┌─────────────────────────────────┐
│           MARGIN                │
│   ┌─────────────────────────┐   │
│   │        BORDER           │   │
│   │   ┌─────────────────┐   │   │
│   │   │    PADDING      │   │   │
│   │   │   ┌─────────┐   │   │   │
│   │   │   │ CONTENT │   │   │   │
│   │   │   └─────────┘   │   │   │
│   │   └─────────────────┘   │   │
│   └─────────────────────────┘   │
└─────────────────────────────────┘

Unit Recommendations

Code Examples

Selector Efficiency

/* Efficient: Single class */
.nav-link { }

/* Less efficient: Descendant chain */
nav ul li a { }

/* Prefer attribute selectors */
[data-state="active"] { }

Box Model Reset

*, *::before, *::after {
  box-sizing: border-box;
}

* {
  margin: 0;
  padding: 0;
}

Test Template

describe('CSS Fundamentals Skill', () => {
  test('validates topic parameter', () => {
    expect(() => skill({ topic: 'invalid' }))
      .toThrow('Topic must be one of: selectors, specificity...');
  });

  test('returns selector examples for selectors topic', () => {
    const result = skill({ topic: 'selectors', level: 'beginner' });
    expect(result).toContain('.class');
    expect(result).toContain('#id');
  });

  test('handles missing optional parameters', () => {
    const result = skill({ topic: 'box-model' });
    expect(result.level).toBe('beginner');
    expect(result.include_examples).toBe(true);
  });
});

Error Handling

Related Skills

• css-flexbox-grid (layout builds on fundamentals)
• css-architecture (naming builds on selectors)
• css-modern (extends selector knowledge)

Css Fundamentals Guide

Overview

This guide provides comprehensive documentation for the css-fundamentals skill in the custom-plugin-css plugin.

Category: General

Quick Start

Prerequisites

• Familiarity with general concepts
• Development environment set up
• Plugin installed and configured

Basic Usage

# Invoke the skill
claude "css-fundamentals - [your task description]"

# Example
claude "css-fundamentals - analyze the current implementation"

Core Concepts

Key Principles

1. Consistency - Follow established patterns 2. Clarity - Write readable, maintainable code 3. Quality - Validate before deployment

Best Practices

• Always validate input data
• Handle edge cases explicitly
• Document your decisions
• Write tests for critical paths

Common Tasks

Task 1: Basic Implementation

# Example implementation pattern
def implement_css_fundamentals(input_data):
    """
    Implement css-fundamentals functionality.

    Args:
        input_data: Input to process

    Returns:
        Processed result
    """
    # Validate input
    if not input_data:
        raise ValueError("Input required")

    # Process
    result = process(input_data)

    # Return
    return result

Task 2: Advanced Usage

For advanced scenarios, consider:

• Configuration customization via assets/config.yaml
• Validation using scripts/validate.py
• Integration with other skills

Troubleshooting

Common Issues

Related Resources

• SKILL.md - Skill specification
• config.yaml - Configuration options
• validate.py - Validation script

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Last updated: 2025-12-30

Css Fundamentals Patterns

Design Patterns

Pattern 1: Input Validation

Always validate input before processing:

def validate_input(data):
    if data is None:
        raise ValueError("Data cannot be None")
    if not isinstance(data, dict):
        raise TypeError("Data must be a dictionary")
    return True

Pattern 2: Error Handling

Use consistent error handling:

try:
    result = risky_operation()
except SpecificError as e:
    logger.error(f"Operation failed: {e}")
    handle_error(e)
except Exception as e:
    logger.exception("Unexpected error")
    raise

Pattern 3: Configuration Loading

Load and validate configuration:

import yaml

def load_config(config_path):
    with open(config_path) as f:
        config = yaml.safe_load(f)
    validate_config(config)
    return config

Anti-Patterns to Avoid

❌ Don't: Swallow Exceptions

# BAD
try:
    do_something()
except:
    pass

✅ Do: Handle Explicitly

# GOOD
try:
    do_something()
except SpecificError as e:
    logger.warning(f"Expected error: {e}")
    return default_value

Category-Specific Patterns: General

Recommended Approach

1. Start with the simplest implementation 2. Add complexity only when needed 3. Test each addition 4. Document decisions

Common Integration Points

• Configuration: assets/config.yaml
• Validation: scripts/validate.py
• Documentation: references/GUIDE.md

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Pattern library for css-fundamentals skill