---
name: interior-design-principles
description: |
  Applies core interior design principles -- scale, proportion, color theory, lighting, and traffic flow -- to residential room layouts. Produces a design assessment with specific recommendations for furniture arrangement, color palette, and lighting plan.
  Use when the user asks about room layout, furniture arrangement, color schemes for rooms, lighting design for living spaces, or how to make a room feel larger, cozier, or more functional.
  Do NOT use for commercial interior design, architectural modifications, renovation budgeting (use renovation-budget instead), or choosing specific furniture products.
license: Apache-2.0
metadata:
  author: foundry-skills
  version: "1.0.0"
  tags: "design planning budgeting"
  category: "home-household"
  subcategory: "interior-organization"
  depends: ""
  disclaimer: "none"
  difficulty: "intermediate"
---
# Interior Design Principles

## When to Use

**Use this skill when:**
- A user describes a room and asks how to arrange or rearrange furniture, including which pieces to keep, move, or eliminate
- A user wants a color palette, color scheme, or paint color direction for a specific room (including guidance on which walls to treat, how many colors to use, and how colors interact with their light conditions)
- A user says a room feels "off," "cold," "too big," "cramped," "dark," "boring," "sterile," or "chaotic" and cannot identify why
- A user wants a lighting plan -- which fixture types to choose, where to place them, what color temperatures to use, and how many lumens the room needs
- A user has a specific design challenge: no focal point, awkward room shape (L-shaped, very narrow, oddly proportioned), low ceilings, too many doorways, or conflicting furniture styles they want to unify
- A user wants to make a room feel larger, cozier, taller, more intimate, or more functional through design choices rather than renovation
- A user wants to understand design principles so they can make their own decisions about a room -- the educational application of this skill

**Do NOT use when:**
- The user needs to calculate renovation costs, select contractors, or plan a construction sequence -- use `renovation-budget` instead
- The user is ready to purchase specific paint products and needs step-by-step application guidance -- use `paint-a-room` for execution
- The user is selecting flooring materials for a renovation project -- use `flooring-selection`
- The user is designing a commercial space, office, restaurant, retail environment, or hospitality venue -- these require code compliance, ADA standards, and commercial ergonomics outside this skill's scope
- The user wants specific furniture product recommendations, brand comparisons, or retailer sourcing -- this skill governs principles and placement, not procurement
- The user is making structural changes -- removing walls, adding windows, changing ceiling height -- which are architectural decisions governed by load-bearing engineering, not design principles

---

## Process

### Step 1: Gather Room Intelligence

Before applying any principle, collect the following information. Incomplete data leads to generic advice; complete data enables precision.

- **Dimensions:** Length, width, and ceiling height. If the user does not know exact measurements, ask them to pace the room (1 adult pace ≈ 2.5 feet) or measure with a phone's built-in measurement app. Ceiling height matters because rooms under 8 feet need different treatments than rooms over 10 feet.
- **Room shape:** Rectangular is standard. Flag L-shaped, square (aspect ratio under 1.2:1), very narrow (aspect ratio over 2.5:1), or rooms with alcoves and bump-outs -- each requires a different layout strategy.
- **Window inventory:** Count, approximate size, and cardinal direction (north/south/east/west). This governs the entire color and lighting strategy. A north-facing room with one small window behaves completely differently from a south-facing room with a window wall.
- **Existing furniture the user plans to keep:** Get the approximate dimensions if possible -- especially sofa length, bed size, and dining table dimensions, since these are the anchors around which all other decisions scale.
- **Room function:** Primary and secondary use. A room used for TV watching requires different sightline geometry than a room used for conversation. A home office/guest room split requires zone planning.
- **Entry point and traffic patterns:** Where is the door? Are there multiple entry points? What rooms does this space connect to? Is there a hallway that feeds into it? This defines non-negotiable pathway corridors.
- **Pain points:** Ask the user directly what feels wrong. Their answer reveals which principles to prioritize. "Too cold" points to color temperature and textile mass. "Too dark" points to lighting layers and reflective surfaces. "Feels like a hotel lobby" points to missing human scale and personal elements.
- **Budget tier:** Refresh (under $500, mostly rearrangement plus accessories), Moderate ($500-$2,000, paint plus new lighting plus key textiles), Full ($2,000+, new anchor furniture pieces). This gates which solutions are available.

---

### Step 2: Analyze Scale and Proportion

Scale is the relationship between furniture size and room size. Proportion is the relationship between furniture pieces relative to each other. Both must be correct for a room to feel balanced.

**Scale analysis -- absolute rules with measurements:**
- Sofa length should be 2/3 to 3/4 the length of the wall it sits against. A sofa on a 14-foot wall should be 9.3 to 10.5 feet -- either a large sectional or a sofa plus a loveseat grouped together. A 6-foot sofa in that position reads as undersized regardless of how it is arranged.
- Coffee table length should be 1/2 to 2/3 the sofa length, and height should be within 2 inches of the sofa seat height (typically 16-18 inches). A coffee table that is too small for the sofa creates the "floating island" problem.
- Area rugs are the single most common scale error. In a living room, use an 8x10 or 9x12 rug as the default. A 5x8 rug in a standard living room is almost always too small. The rug should either have all front furniture legs on it (minimum) or all four legs of every piece on it (preferred).
- Nightstands should be within 2 inches of mattress surface height. A bed with a 25-inch platform height paired with 18-inch nightstands creates a visual imbalance that reads as clumsy.
- Dining tables: allow exactly 24 inches of table edge width per place setting, 36 inches from table edge to wall for chair pullout and walker passage (30 inches is the absolute minimum in tight spaces).
- Art placement: center of artwork should sit at 57-60 inches from the floor -- this is the standard gallery hanging height and the average human eye level. Over a sofa, artwork should be 2/3 to 3/4 the width of the sofa and hung 6-8 inches above the sofa back.

**Proportion analysis -- relative rules:**
- The 60-30-10 color rule governs color proportion: 60% dominant (walls, large upholstery, flooring), 30% secondary (curtains, secondary furniture, bedding), 10% accent (pillows, art, decorative objects). Violating this rule -- for example, 50-25-25 -- eliminates hierarchy and creates visual noise.
- Vary furniture heights deliberately. A room where every piece of furniture tops out at 32-36 inches (sofa arm height) reads as flat and monotonous. Introduce at least one tall element -- a bookcase, floor lamp, or tall plant -- that reaches 60+ inches and anchors vertical space.
- In rooms under 150 square feet, cap major furniture at 4 pieces. Every additional piece after the fourth compounds the cramped feeling exponentially, not linearly.
- In rooms over 300 square feet, furniture pushed against all walls creates a "waiting room" effect with a dead center. Float furniture groupings at least 12-18 inches from the wall to create human-scaled zones.
- The "big piece first" rule: place the largest piece of furniture first, then scale every other piece relative to it. Placing the coffee table before determining sofa placement is the most common amateur layout error.

---

### Step 3: Develop the Color Palette

Color selection is governed by light physics, not preference alone. A user who loves gray-blue walls in a showroom may get a dungeon in their north-facing room. Ground every color recommendation in the room's actual light conditions.

**Step 3a: Determine the room's light character:**

| Window Direction | Natural Light Quality | Dominant Color Cast | Design Implication |
|-----------------|----------------------|--------------------|--------------------|
| North-facing | Consistent, cool, diffuse -- no direct sun | Blue-gray cast throughout the day | Warm tones essential to compensate; avoid cool grays and blue-whites, which amplify the chill |
| South-facing | Warm, golden, direct -- floods the room most of the day | Amber/gold cast in afternoon | Highly versatile; cool tones stay balanced; deep colors work here because they receive enough light |
| East-facing | Warm golden light until ~11am, then cool and neutral all afternoon | Shifts from warm to cool daily | Use neutral-warm tones that read consistently under both light conditions; avoid strong cool tones |
| West-facing | Cool and dim in the morning, intensely warm and orange from 3pm onward | Strong orange-red cast in late afternoon | Cool to neutral tones prevent afternoon overheating; warm tones can become overpowering at 4-6pm |

**Step 3b: Build the palette using the 60-30-10 framework:**
- **Dominant color (60%):** This is the visual "ground" of the room -- walls, large area rug, or dominant upholstery. Choose based on the room's light character above. The dominant color sets the emotional tone: warm tones (cream, terracotta, warm taupe, sage) create comfort; cool tones (slate, soft gray-blue, greige) create calm.
- **Secondary color (30%):** This appears in upholstery, curtains, the second-largest furniture piece, or bedding. It should either harmonize with the dominant (analogous -- within 60 degrees on the color wheel) or contrast it (complementary -- 150-180 degrees on the color wheel). A complementary secondary creates energy; an analogous secondary creates flow.
- **Accent color (10%):** This is the "voice" of the room and should be the highest-saturation color in the palette. It appears in pillows, art, small decorative objects, lamp shades, and trim details. In a room with muted dominant and secondary colors, the accent can be bold -- cobalt, saffron, rust, emerald -- without overwhelming.

**Step 3c: Apply color to perceived room dimensions:**

| Technique | Effect | Specific Application |
|-----------|--------|---------------------|
| Monochromatic wall and trim (same color family) | Walls appear to recede; room reads as larger | Paint trim 1-2 shades lighter than the wall color instead of stark white trim on colored walls |
| Dark accent wall on the far wall from entry | Adds depth; draws the eye; makes room feel longer | Use a color 3-4 LRV (Light Reflectance Value) points darker than adjacent walls |
| Low LRV (<30) on all 4 walls | Room closes in; creates cozy effect | Use in large rooms (300+ sqft) or rooms with very high ceilings (10ft+) deliberately |
| High LRV (>70) on walls and ceiling | Maximizes perceived size | Ceiling color should be 1 shade lighter than walls, not stark white, to avoid "floating lid" look |
| Ceiling painted darker than walls | Lowers perceived ceiling height by 1-2 feet visually | Use in rooms with ceilings over 9 feet to create intimacy |
| Horizontal color banding or two-tone walls | Makes walls appear wider | Color break at 36-48 inches from floor; lower half darker, upper half lighter |

**Step 3d: Undertone matching is non-negotiable:**
Every white, gray, and beige has an undertone (pink, purple, green, yellow, blue). The dominant color's undertone must harmonize with the fixed elements of the room -- flooring color, existing furniture finishes, tile, brick, and woodwork. A gray with purple undertones next to warm honey-oak flooring creates an invisible but persistent visual discomfort. Identify undertones by comparing the color chip to a pure white card: whatever color the chip appears to "lean toward" is its undertone.

---

### Step 4: Design the Lighting Plan

Lighting is the most underutilized design tool in residential spaces. Most rooms are lit with a single overhead fixture that creates flat illumination, harsh shadows, and a visual monoculture. Layer three types of lighting to transform any room.

**The three lighting layers:**

| Layer | Function | Fixture Examples | Placement Logic |
|-------|---------|----------------|----------------|
| Ambient (General) | Overall room brightness; replaces daylight | Ceiling fixtures, recessed downlights, semi-flush mount, chandelier, cove lighting | Centered, evenly distributed; avoid placing recessed lights directly over seating (creates unflattering downlight on faces) |
| Task | Focused light for specific activities | Desk lamp, pharmacy lamp, reading floor lamp, under-cabinet strip, pendant over island | Positioned to illuminate the work surface without casting shadow from the user's own body |
| Accent | Highlights objects, adds depth and drama | Wall sconces, picture lights, uplights, LED strip behind TV or floating shelves, candles, battery-operated puck lights | Aimed at art, architectural features, bookcases, or plants to create visual hierarchy |

**Lighting measurements and specifications:**

- **Lumen budgeting:** Use 20 lumens per square foot for ambient lighting as a baseline. Living rooms and bedrooms: 10-20 lumens/sqft (lower end for intimacy). Kitchens: 30-40 lumens/sqft. Home offices: 40-50 lumens/sqft for task areas.
- **Color temperature:** 2700K (warm white) for living rooms, bedrooms, dining rooms -- this is the closest to incandescent warmth and creates a flattering, inviting environment. 3000K for kitchens, bathrooms, home offices where clarity matters without harshness. 4000K+ only in dedicated workspaces or garages. Mixing color temperatures in one room (e.g., 2700K lamps + 5000K overhead) is a common and jarring mistake.
- **Dimmer switches:** Every ambient circuit in a living room, bedroom, or dining room should have a dimmer. This single $15-$30 hardware change converts a fixed-brightness room into a multi-mood space.
- **The rule of thirds for floor lamps:** Place floor lamps in corners or at the junction of seating pieces to push light up into the corners of the room -- ceiling corners receive the least light from center fixtures, and illuminating them visually expands the room.
- **Lamp scale:** Table lamp height should be proportional to the surface it sits on. A lamp's bottom of the shade should sit at approximately eye level when seated (about 38-42 inches from floor for standard seating). Lamp shade diameter should be roughly equal to 2/3 the lamp base height.
- **Recessed lighting placement:** Space recessed downlights at 1.5 times the ceiling height apart. In a 9-foot ceiling, space cans at 13-14 feet apart center-to-center. Position cans 24-30 inches from walls to wash the walls with light rather than creating a center spotlight effect.

---

### Step 5: Establish Traffic Flow and Pathway Clearances

A beautiful room that cannot be navigated comfortably fails at its primary function. Traffic flow analysis is done before finalizing furniture placement -- it defines the non-negotiable channels that furniture must work around.

**Required clearances:**

| Pathway Type | Minimum | Comfortable | Notes |
|-------------|---------|-------------|-------|
| Primary traffic path (main route through room) | 36 inches | 42-48 inches | This is a building code standard for accessibility |
| Secondary path (occasional passage) | 24 inches | 30 inches | Acceptable behind a secondary chair, between bookcase and wall |
| Sofa to coffee table | 14 inches | 16-18 inches | Under 14 inches forces knees-together awkwardness; over 20 inches requires leaning forward uncomfortably |
| Dining chair to wall or adjacent furniture | 30 inches (absolute min) | 36-48 inches | 36 inches allows chair pullout + comfortable passage; 48 inches allows two people to pass |
| Bed to wall (walking side) | 24 inches | 30-36 inches | 24 inches is the minimum for dressing without turning sideways |
| Bed to wall (non-walking/window side) | 12 inches | 18-24 inches | Allows bed-making but not regular passage |
| Around a desk chair | 30 inches (behind) | 36 inches | Allows rolling back and standing without obstruction |

**Focal point principles:**
- Every room must have exactly one primary focal point. Multiple competing focal points create visual chaos. In a room with both a fireplace and a large TV, decide which is primary and position seating toward it; subordinate the other.
- The focal point should be visible from the room's entry point. The first thing a person sees when entering establishes the room's identity.
- If no architectural focal point exists (no fireplace, no significant window, no architectural feature), create one: a gallery wall sized to fill 2/3 to 3/4 of the wall width it occupies, a large-scale artwork (minimum 30x40 inches in a standard living room), or a bold paint treatment on the primary wall.
- Seating conversation distance: 4-8 feet between facing seating pieces for comfortable conversation without raised voices. Beyond 8 feet, the arrangement functions as separate zones rather than a unified conversation area.

**The furniture float rule:**
Pushing all furniture against the walls creates a "conversation pit" effect with empty dead space in the center. In rooms 12 feet wide or wider, float the sofa at least 12 inches from the wall. The trade-off is a walkable path behind the sofa -- which actually improves traffic flow in many room configurations.

---

### Step 6: Apply Balance, Rhythm, and Emphasis

These are the "invisible" principles that distinguish a room that "looks like a magazine" from one that merely has good furniture.

**Types of balance:**
- **Symmetrical balance:** Identical or near-identical elements on either side of a central axis (matching nightstands, matching lamps flanking a sofa, twin chairs on either side of a fireplace). Creates formality and calm. Works best in traditional and transitional styles.
- **Asymmetrical balance:** Different objects of similar visual weight on either side of an axis (a tall lamp on one side balanced by a lower console with a grouping of objects on the other). Creates dynamism and is more forgiving of mismatched existing furniture. More difficult to execute but more interesting.
- **Radial balance:** Elements arranged around a central point (round dining table with chairs, circular rug centered under a chandelier). Creates a natural focal energy. Often underused in residential design.

**Visual weight principles:**
- Dark, heavy textures (leather, velvet, solid wood) carry more visual weight than light, airy materials (linen, glass, lucite).
- Tall vertical elements carry visual weight upward; horizontal elements spread weight across a surface.
- A cluster of small objects can visually balance one large object -- group in odd numbers (3 or 5 objects) for the most natural-looking arrangement.
- Balance visual weight across the room diagonally as well as side-to-side. If the heaviest visual element is in one corner, introduce something with comparable visual presence in the opposite corner.

**Rhythm and repetition:**
- Repeat a color, shape, or material at least 3 times in a room to create intentional rhythm. A single orange throw pillow reads as an accident; orange in the pillow, echoed in a ceramic vase, and picked up in a print on the wall reads as a design decision.
- Vary the scale of repeated elements: the same color in a large rug, a medium pillow, and a small decorative object creates rhythm without monotony.

---

### Step 7: Assemble the Design Recommendation

Synthesize all analysis into a prioritized, actionable plan that addresses the user's pain points first, then optimizes for aesthetics.

- Lead with the single highest-impact change for this specific room and this specific pain point. Justify it with the principle it applies.
- Sequence remaining recommendations by impact-to-cost ratio. A $25 dimmer switch that transforms evening ambiance ranks above a $200 decorative object.
- Flag any existing furniture pieces that are actively working against the design and explain why specifically -- "your 5-foot sofa reads as undersized in this 14-foot room because it leaves 4.5 feet of awkward dead space on either side."
- Provide the budget estimate with realistic ranges, not aspirational minimums.

---

## Output Format

```
## Interior Design Plan: [Room Type] ([Dimensions], [Ceiling Height], [Window Direction])

### Room Assessment
| Design Parameter   | Current Status                        | Core Problem                           | Recommendation                         |
|--------------------|---------------------------------------|----------------------------------------|----------------------------------------|
| Scale              | [existing furniture scale observation] | [specific scale issue]                 | [specific correction with measurement] |
| Proportion         | [how pieces relate to each other]     | [proportion imbalance identified]      | [specific correction]                  |
| Color              | [current palette and light conditions] | [color theory issue]                   | [specific palette direction]           |
| Lighting           | [current layer inventory]             | [missing layers or wrong temperatures] | [specific additions with spec]         |
| Traffic Flow       | [current pathway widths observed]     | [clearance violations or dead zones]   | [specific layout correction]           |
| Focal Point        | [current focal point or absence]      | [focal point problem]                  | [specific focal point solution]        |
| Balance            | [current balance type]                | [balance issue]                        | [specific balance correction]          |

### Color Palette
| Role            | Color Description       | LRV Range  | Undertone   | Where to Apply                          |
|-----------------|------------------------|------------|-------------|----------------------------------------|
| Dominant (60%)  | [color name + family]  | [LRV]      | [undertone] | [walls, large area rug, dominant upholstery] |
| Secondary (30%) | [color name + family]  | [LRV]      | [undertone] | [curtains, secondary furniture, accent chair, bedding] |
| Accent (10%)    | [color name + family]  | [LRV]      | [undertone] | [pillows, art, ceramics, lamp shade]   |

**Special treatment:** [ceiling color direction] | [trim treatment] | [any accent wall specification]

**Light interaction note:** [How these colors will behave in this room's specific light conditions]

### Furniture Layout
**Anchor placement (largest piece first):**
- [Primary piece]: [placement description with wall reference and distance from wall]
- [Secondary piece]: [placement relative to primary, with gap measurement]
- [Tertiary piece]: [placement with gap measurements from adjacent pieces]
- Area rug: [size recommendation, placement logic, how many furniture legs on rug]

**Traffic paths:**
- Primary path: [route description] -- [clearance width] clear
- Secondary path: [route description] -- [clearance width] clear

**Clearance checks:**
- [Sofa to coffee table]: [measurement]
- [Dining chairs to wall, if applicable]: [measurement]
- [Bed to wall on walking sides, if applicable]: [measurement]

### Lighting Plan
| Layer   | Fixture Type         | Location                    | Color Temp | Lumens     | Notes                           |
|---------|---------------------|-----------------------------|------------|------------|---------------------------------|
| Ambient | [type]              | [specific location]         | [K rating] | [target]   | [dimmer? Switch location?]      |
| Task    | [type]              | [specific location]         | [K rating] | [target]   | [height, shade size, direction] |
| Accent  | [type]              | [specific location]         | [K rating] | [target]   | [what it highlights]            |

**Total estimated ambient lumens:** [calculated total] vs. [target based on sqft]

### Balance and Emphasis
- Focal point: [what it is, where it sits, why it commands the room]
- Balance type: [symmetrical/asymmetrical/radial] -- [specific axis or center point]
- Rhythm element: [which color, shape, or material repeats, and where]
- Vertical anchor: [what tall element grounds the vertical space and where]

### Priority Action Plan
| Priority | Change                         | Design Principle Applied         | Budget Impact  |
|----------|-------------------------------|----------------------------------|----------------|
| 1        | [specific action]             | [principle: scale/color/etc.]    | $[range]       |
| 2        | [specific action]             | [principle]                      | $[range]       |
| 3        | [specific action]             | [principle]                      | $[range]       |
| 4        | [specific action]             | [principle]                      | $[range]       |
| 5        | [specific action]             | [principle]                      | $[range]       |

### Estimated Budget
| Item                        | Cost Range     | Priority  |
|-----------------------------|----------------|-----------|
| [Item 1]                   | $[min]-$[max]  | Essential |
| [Item 2]                   | $[min]-$[max]  | High      |
| [Item 3]                   | $[min]-$[max]  | Medium    |
| [Item 4]                   | $[min]-$[max]  | Nice-to-have |
| **Total Range**            | **$[X]-$[Y]**  |           |

### What to Avoid
- [Specific mistake this user is most likely to make, with explanation of why]
- [Second common mistake in this room configuration]
- [Third mistake based on existing furniture/conditions]
```

---

## Rules

1. **Never give a color recommendation without first identifying the window direction.** Color perception is dominated by natural light. A warm greige that looks sophisticated in a south-facing room looks dingy in a north-facing room. If the user does not know their window direction, ask -- or instruct them to use a compass app on their phone.

2. **Never recommend a rug smaller than 8x10 for a standard living room.** The 5x8 rug error is the single most common scale mistake in residential design. If the user's budget does not allow an appropriately sized rug, recommend a natural fiber flatweave (jute, sisal, seagrass) in the correct size over a small premium rug.

3. **Always address the pain point before the aesthetic optimization.** If the user says the room feels dark, the lighting plan comes before the color palette discussion. If the room feels cramped, traffic flow and furniture scale come before accent wall recommendations. Aesthetic improvements that ignore the functional problem feel hollow.

4. **Apply the 60-30-10 color rule with LRV awareness, not just hue awareness.** A room where the dominant, secondary, and accent colors all have LRV values within 10 points of each other will feel flat regardless of hue variety. Build contrast through LRV spread: at minimum 20 LRV points between dominant and accent.

5. **Always specify color temperature (Kelvin) alongside any lighting recommendation.** A recommendation to "add a floor lamp" without specifying 2700K versus 4000K can actively worsen the room's atmosphere. Mismatched color temperatures in the same room are visually jarring and defeat the purpose of layered lighting.

6. **Check sofa-to-coffee-table clearance every time.** The 14-18 inch sweet spot is the most frequently violated furniture spacing rule. At 12 inches, knees hit the table when sitting back; at 22+ inches, users lean uncomfortably to reach surfaces. Flag this proactively if the user mentions having a coffee table.

7. **Scale budget recommendations to what the user stated.** A user with a $500 budget who asks about making their room feel better does not want a plan that requires $3,000 in new furniture. Lead with what can be accomplished within the stated budget; flag what would require additional investment only as an optional next tier.

8. **Identify the focal point before placing a single piece of furniture.** All furniture arrangement radiates outward from the focal point. If the focal point changes, the entire layout may need to change. Settling this first prevents the most common layout errors.

9. **Never recommend pushing all furniture against the walls in a room 12 feet wide or wider.** This creates a "waiting room" layout with dead center space and seating that is too far apart for conversation. Float the primary seating group even if it feels counterintuitive to the user.

10. **Distinguish between what exists and what is fixable.** If the user has a brown leather sofa they will not replace, the palette must work with brown leather -- not around it or despite it. Identify the fixed elements first (flooring, existing furniture being kept, permanent fixtures) and treat them as constraints, not problems. Every palette built must harmonize with these non-negotiables.

---

## Edge Cases

**Studio apartment or open floor plan (under 600 sqft with no walls separating zones):**
Define separate zones using three tools: area rugs (each zone gets its own rug, clearly delineating its footprint), lighting (each zone has its own ambient or task light source, not shared from one central overhead), and furniture orientation (a sofa placed perpendicular to the long wall acts as a visual wall between living and dining zones). Maintain one unified color palette across zones -- changing the palette at the zone boundary makes the space feel fractured. Instead, vary accent colors: warm amber in the living zone, cool blue in the sleeping or office zone, while sharing the same dominant neutral. Ceiling height in studios is often below 8 feet; avoid tall, heavy furniture. Use furniture with visible legs throughout to expose floor and increase perceived square footage.

**Very small room (under 100 square feet):**
The design goal shifts from aesthetic optimization to perceptual expansion. Every choice must serve this goal. Use mirrors strategically: a mirror placed opposite or adjacent to the primary window doubles the perceived natural light and creates the illusion of depth. Mirrors should be large-scale -- at minimum 24x36 inches -- to be effective; small decorative mirrors are functionally useless for spatial expansion. Choose furniture with visible legs, lucite or glass elements, and light-value finishes. Mount lighting on the wall or ceiling rather than using floor lamps, which consume floor real estate. Limit the palette to 2-3 colors maximum; a fourth color in a small room reads as clutter. Use vertical space: floating shelves from 6 feet to ceiling, tall narrow bookcases, and wall-mounted art stacked vertically rather than spread horizontally.

**Room with no windows or only borrowed light (interior room, basement, windowless bedroom):**
Artificial lighting is not a supplement here -- it is the entire light design challenge. Target 35-40 lumens per square foot rather than the standard 20, because there is no ambient daylight contribution. Use 3000K-3500K lighting throughout rather than 2700K -- in the complete absence of daylight, 2700K reads as dim and cave-like rather than warm and inviting. Place a large mirror (minimum 24 inches wide) on the wall opposite the primary light source to reflect and multiply the light. Use high-LRV (70+) wall colors -- not necessarily white, but any light value -- because dark walls in a windowless room create a clinically uncomfortable environment regardless of aesthetic intent. Avoid velvet, dark wood, and heavy textures as dominant materials; they absorb rather than reflect what little light exists.

**Multi-function room (home office + guest room, playroom + family room, dining room + home office):**
Zoning is the critical strategy. Each function requires: its own defined footprint (via rug or furniture boundary), its own task lighting, and storage to contain its own materials out of sight. The primary function owns the better position in the room -- better light, better traffic flow, better sightlines. The secondary function uses concealment: a Murphy bed folds away, a desk can be positioned behind the sofa and cordoned off by a narrow shelving unit, a play area uses storage ottomans to collapse toys quickly. If the two functions have incompatible aesthetic requirements (a professional home office setup alongside a cozy family space), let the dominant finish -- flooring, wall color, primary textiles -- serve the primary function, and let the secondary function's character come from its contained zone accessories.

**Rental with no permanent modifications allowed:**
The design toolkit narrows to: textiles, lighting, and removable surface treatments. Textiles (area rugs, curtains, throw blankets, pillow covers) are the highest-impact tool -- they add color, texture, warmth, and acoustic softness without any permanence. Curtains hung from tension rods (which require no drilling) can transform a window entirely. Floor lamps and table lamps replace any fixture changes. Removable peel-and-stick wallpaper applied to one accent wall achieves 80% of the impact of paint at roughly equivalent cost, and modern products remove cleanly from standard drywall. Art installation without wall damage: use oversized leaned art (a large canvas or framed piece leaning against the wall on a console or floor) for gallery-quality presence with no holes. Command-strip picture hangers hold up to 16 pounds per strip, suitable for most art pieces.

**Awkward room shape (L-shaped, very narrow, or oddly proportioned):**
L-shaped rooms have two distinct zones joined at the bend -- treat them as two related rooms with a shared palette rather than one room with a strange shape. The larger zone takes the primary function; the smaller zone takes the secondary function. Place a rug in each zone. Very narrow rooms (aspect ratio greater than 2.5:1 -- for example, a 10x25 foot room) benefit from a strong dark accent wall on the short end, which optically "pulls" the far wall closer and reduces the tunnel effect. Horizontal striping on the long walls (a paint color break at 36 inches, or a chair rail with two-tone treatment) visually widens the room. Avoid placing furniture along both long walls in opposition -- this reinforces the narrow bowling-alley shape. Instead, angle furniture 30-45 degrees to create diagonal interest and interrupt the tunnel geometry.

**Room with too many doorways or architectural interruptions:**
A room with three or four doorways has almost no uninterrupted wall runs, which creates placement nightmares for large furniture. The solution is to identify the longest uninterrupted wall section and make that the anchor wall for the primary furniture piece, even if that wall section is only 8-10 feet. Work with the interruptions: a low console placed between two doorways keeps sightlines open while filling the gap. Consider whether any of the doorways are rarely used -- if so, a piece of furniture placed in front of a secondary door (while still allowing the door to open) can visually "close" that wall and simplify the layout logic significantly.

---

## Example

**User input:** "My bedroom is 12 feet by 15 feet with 8-foot ceilings. There's one east-facing window, maybe 3 feet wide. The walls are a cool gray and it feels really cold and kind of hospital-like. I have a queen bed, two mismatched nightstands (one is dark walnut, one is white), and a low white dresser. I really want it to feel cozy and warm. Budget is $300-$600."

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## Interior Design Plan: Primary Bedroom (12x15, 8ft ceilings, East-facing window)

### Room Assessment
| Design Parameter   | Current Status                          | Core Problem                               | Recommendation                                  |
|--------------------|-----------------------------------------|--------------------------------------------|------------------------------------------------|
| Scale              | Queen bed is appropriately scaled for 12x15; white dresser likely undersized if below 48 inches wide | Dresser may read as too small on the 12-foot wall | Assess dresser width -- if under 48 inches, layer a large mirror above it to increase visual mass |
| Proportion         | Two mismatched nightstands (dark walnut + white) create asymmetrical imbalance | The mismatch is creating visual noise rather than intentional asymmetry | Unify with matching lamps and coordinating accessories to create visual rhythm across the mismatch |
| Color              | Cool gray walls in an east-facing room -- cool morning light + cool afternoon light double down on the gray's cool cast | The gray is selecting for its blue/purple undertone all day in east-facing light, creating the hospital feel | Replace with a warm, mid-value color: warm taupe, soft terracotta-adjacent beige, or warm sand |
| Lighting           | Likely one overhead fixture only | Single overhead light at 8 feet creates institutional flatness with no warmth in the evening | Add task layer (reading lamps on nightstands) and accent layer (warm LED strip behind bed or uplight behind dresser mirror) |
| Traffic Flow       | 12-foot wide room with queen bed (60 inches wide) leaves 36 inches total for both walking sides -- workable but tight | If dresser is on the 12-foot wall opposite the bed, verify 24-inch minimum clearance on both bed sides | Center the bed on the 15-foot wall to maximize walking clearance; aim for 28-30 inches on each walking side |
| Focal Point        | No clear focal point identified -- mismatched nightstands pull attention to the mismatch | The bed should be the obvious focal point in a bedroom; it currently competes with visual clutter | Create a statement bed wall with warm tone paint treatment, artwork above headboard, and symmetrical lamp placement |
| Balance            | Currently asymmetrical (mismatched nightstands) without intentional design | Unintentional asymmetry reads as incomplete rather than dynamic | Convert to working asymmetrical balance: use the walnut nightstand's warmth and the white one's lightness as anchors, tied together by matching lamps |

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### Color Palette

| Role            | Color Description            | LRV Range  | Undertone     | Where to Apply                                |
|-----------------|------------------------------|------------|---------------|----------------------------------------------|
| Dominant (60%)  | Warm sand / soft linen beige | 65-72      | Yellow-cream  | All four walls -- this is a full-room change, not an accent |
| Secondary (30%) | Warm ivory / natural linen   | 78-84      | Cream/yellow  | Bedding (duvet, sheets), curtain panels, any upholstered bench if present |
| Accent (10%)    | Burnt sienna / rust-adjacent terracotta | 28-38 | Orange-red | Throw pillows (3-4), one or two ceramics on dresser top, artwork mat |

**Special treatment:** Ceiling -- paint 1-2 shades lighter than the wall color (LRV 75-78) rather than stark white. This keeps the ceiling warm and maintains the cozy feel without the clinical white-lid effect. Trim can remain white or shift to a warm off-white (avoid pure blue-white trim, which will conflict with the new warm wall). No accent wall needed -- the warm sand will read uniformly warm in east-facing light and provide enough shift from the current cool gray.

**Light interaction note:** In east-facing light, warm yellow-cream undertones will activate beautifully in the morning and hold their warmth through the afternoon without going dull. The previous cool gray was selecting for its blue-purple undertone in the same light conditions. The burnt sienna accent will pick up gold in morning light, making it feel especially rich.

---

### Furniture Layout

**Anchor placement (largest piece first):**
- Queen bed (60 inches wide): Center the headboard on the 15-foot wall that is opposite the entry door or the primary sightline from the doorway. This makes the bed the first thing seen when entering -- correct for bedroom focal point. Pulled 2 inches from the wall (not floating, but not hard against it).
- Dark walnut nightstand (existing): Left side of bed, positioned so its top surface is within 2 inches of mattress surface height. If it is significantly taller or shorter than the mattress surface, add or remove a tray to adjust perceived height.
- White nightstand (existing): Right side of bed. The mismatch is redeemed by placing matching table lamps on both -- the eye reads "matching lamps over different tables" as an intentional collected look rather than an oversight.
- White dresser: Place on the 12-foot wall perpendicular to the bed wall, rather than directly opposite the bed (which can feel confrontational in small bedrooms). Position a mirror above it -- vertically oriented, at least 24 inches wide, hung so the bottom of the mirror is 6-8 inches above the dresser top. This adds vertical height and reflects the window light back into the room.

**Traffic paths:**
- Primary path (entry door to bed walking side): Target 32-36 inches clear -- achievable by centering the bed on the 15-foot wall (15 feet = 180 inches; queen bed = 60 inches + 2 nightstands at approximately 20 inches each = 100 inches total, leaving 80 inches / 2 sides = 40 inches each side including nightstand width)
- Secondary path (dresser access): 30 inches minimum from dresser face to bed frame or any footboard

**Clearance checks:**
- Bed to wall (each walking side): approximately 28-30 inches with centered placement -- adequate for dressing and bed-making
- Dresser to bed: confirm 30+ inches for drawer opening clearance
- Door swing clearance: verify no furniture intersects the door's 90-degree swing arc

---

### Lighting Plan

| Layer   | Fixture Type              | Location                        | Color Temp | Lumens      | Notes                                      |
|---------|--------------------------|----------------------------------|------------|-------------|-------------------------------------------|
| Ambient | Existing ceiling fixture  | Center of room                  | 2700K      | 800-1000 lm | Replace any bulb over 3000K immediately; add dimmer switch |
| Task    | 2 matching table lamps    | One on each nightstand          | 2700K      | 400-500 lm each | Bottom of shade at ~40-42 inches from floor; shade diameter should be 2/3 of lamp base height |
| Accent  | LED warm strip light or single uplight | Behind dresser mirror, or a battery LED strip along the back of a shelf | 2700K | 200-300 lm | Creates warm glow effect; dramatically reduces harsh shadow cast by overhead |

**Total estimated ambient lumens:** Target 1,200-1,800 lumens for 180 sqft at 10 lumens/sqft (bedroom intimacy standard). One overhead at 800-1,000 lm + two nightstand lamps at 400-500 lm each = 1,600-2,000 lm total. On-target or slightly generous, which is appropriate given the single east window providing limited natural light depth in the afternoon.

---

### Balance and Emphasis

- **Focal point:** The bed wall, made intentional by centering the bed, adding coordinated lamps on both nightstands (symmetrical across the bed), and placing artwork 6-8 inches above the headboard. Artwork should be 2/3 to 3/4 the headboard width -- for a 60-inch queen headboard, target a piece or gallery grouping 40-48 inches wide. Warm-toned subject matter -- abstract warm neutrals, botanical, landscape with earth tones -- reinforces the palette.
- **Balance type:** Asymmetrical balance across the bed -- the dark walnut nightstand has more visual weight than the white one, balanced by placing a slightly taller or visually heavier lamp on the white side. The dark nightstand's warmth anchors the left; the lighter one's brightness opens the right.
- **Rhythm element:** Burnt sienna/rust appears in: throw pillows on the bed (3 pillows: 2 matching + 1 lumbar), at least one ceramic or tray object on the dresser top, and in the artwork color story. Three appearances create deliberate rhythm.
- **Vertical anchor:** The mirror above the dresser serves as the vertical anchor on the dresser wall -- it should extend from 6 inches above the dresser top to as close to 6 feet from the floor as the dresser height allows. A 30x40 inch vertical mirror is the minimum; 24x48 is better.

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### Priority Action Plan

| Priority | Change                                          | Design Principle Applied                  | Budget Impact  |
|----------|------------------------------------------------|-------------------------------------------|----------------|
| 1        | Repaint all four walls to warm sand/linen beige | Color temperature + undertone matching for east-facing light | $40-$70 (1-2 gallons + supplies) |
| 2        | Add 2 matching table lamps to nightstands       | Lighting layers (task); visual unification of mismatched nightstands | $60-$140        |
| 3        | Add new bedding in warm ivory/linen + rust accent pillows | 60-30-10 secondary and accent colors; texture and warmth | $80-$180        |
| 4        | Add a vertically oriented mirror above dresser  | Scale (dresser visual mass); light reflection; perceived ceiling height | $40-$100        |
| 5        | Add dimmer switch to existing overhead          | Lighting control; mood modulation          | $15-$30         |

---

### Estimated Budget

| Item                                          | Cost Range      | Priority     |
|-----------------------------------------------|-----------------|--------------|
| Paint -- warm sand/linen, 2 gallons + supplies | $45-$75         | Essential    |
| 2 matching table lamps                        | $60-$140        | Essential    |
| Duvet cover + 2 pillowcases (linen or cotton) | $50-$120        | Essential    |
| 3-4 accent throw pillows (burnt sienna + warm tones) | $40-$90  | High         |
| Vertical mirror (24x36 minimum)               | $40-$100        | High         |
| Dimmer switch                                 | $15-$25         | High         |
| Warm-toned artwork above headboard            | $30-$80         | Medium       |
| LED accent strip or single uplight            | $15-$40         | Nice-to-have |
| **Total Range**                               | **$295-$670**   |              |

*This plan lands within budget at the lower end of the estimate and at the high end if the mirror and artwork skew toward the upper price range. Priority 1-3 alone (paint + lamps + bedding) for approximately $155-$385 will resolve the "cold and hospital-like" problem statement completely.*

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### What to Avoid

- **Do not keep the cool gray walls and try to warm the room with accessories alone.** Textiles and warm lamps will fight a losing battle against cool gray walls in east-facing light -- the wall color is dominating every other element. The paint change is the mandatory first step, not optional.
- **Do not buy a pair of matching nightstands to replace the mismatched ones within this budget.** The $100-$300 that would cost is better spent on paint, lamps, and bedding, which address three design layers. The mismatch is resolved visually by coordinated lamps -- save nightstand replacement for a future budget tier.
- **Do not add a ceiling fan with a built-in light kit as the ambient source.** Fan-integrated lights are almost universally unflattering (too wide a spread, too centered, often limited to non-dimmable bulbs). If the room lacks a fan and one is desired for function, choose a fan with a separate light kit that accepts a dimmable bulb, or decouple the functions entirely by keeping the fan motor and adding separate ambient light from a different circuit.
