feat: implement multi-expression plotting with Desmos-style UI

- Add Expression struct for managing multiple expressions with custom colors
- Implement Desmos-style collapsible sidebar with numbered slots
- Add dark top bar with Save button and branding
- Support all expression types: regular, polar, parametric, implicit, inequalities
- Add fine grid system with axis labels and zoom controls
- Fix color picker positioning to prevent overlap with text inputs
- Add /bigobj compiler flag for MSVC builds

Resolves #15

Author: saumya1317

DESMOS_FEATURES.md

@@ -0,0 +1,138 @@
+# 🎨 ImGraph - Desmos-Style Features
+
+## New Desmos-Like Interface
+
+### ✨ Key Features Implemented
+
+#### 1. **Beautiful Expression Cards**
+- Each expression is displayed in a rounded card (like Desmos)
+- Clean, modern design with proper spacing
+- Light gray background for better readability
+
+#### 2. **Color-Coded Graphs**
+- **10 Beautiful Preset Colors** that cycle automatically:
+  - 🔴 Red (#C74643)
+  - 🔵 Blue (#4080C7)
+  - 🟢 Green (#45A145)
+  - 🟣 Purple (#9749A3)
+  - 🟠 Orange (#ED7D2E)
+  - 🔷 Cyan (#26AEAE)
+  - 🌸 Pink (#E33E96)
+  - 🟤 Brown (#785447)
+  - ⚫ Dark Gray (#333333)
+  - 💚 Teal (#008040)
+
+#### 3. **Color Picker**
+- Click the colored circle next to each expression
+- Customize with any color you want
+- Color instantly updates on the graph
+
+#### 4. **Grid System**
+- Light gray grid lines (like Desmos)
+- Major grid lines every 5 units (darker)
+- Minor grid lines every 1 unit (lighter)
+- Grid automatically scales with zoom
+
+#### 5. **Axis Labels**
+- Numeric labels on both axes
+- Shows coordinate values
+- Labels positioned clearly away from axes
+- Gray color for subtlety
+
+#### 6. **Expression Controls**
+- ☑️ **Checkbox**: Show/hide individual graphs
+- 🎨 **Color Circle**: Click to change color
+- ❌ **Delete Button**: Remove unwanted expressions
+- 📝 **Large Input Box**: More space for complex equations
+
+#### 7. **Smart UI Layout**
+- Left panel: 30% width (expressions)
+- Right panel: 70% width (graph)
+- Proper padding and spacing
+- Rounded corners on all elements
+
+#### 8. **Enhanced Add Button**
+- Large, prominent "+ Add Expression" button
+- Blue color (Desmos style)
+- Hover effects for better UX
+
+#### 9. **Zoom Control**
+- Clean slider at bottom of left panel
+- Range: 10-500 units
+- Smooth zooming
+
+---
+
+## How It Looks Different from Before
+
+### Before (Old UI):
+- Basic text input
+- Single expression only
+- Fixed colors
+- No grid
+- Plain interface
+- Small text boxes
+
+### After (Desmos-Style):
+- ✅ Multiple expressions with individual cards
+- ✅ Color picker for each expression
+- ✅ Beautiful grid system with labels
+- ✅ Show/hide toggle for each expression
+- ✅ Modern, polished interface
+- ✅ Large, easy-to-use input boxes
+- ✅ Preset color palette
+- ✅ Smooth, professional design
+
+---
+
+## Example Usage
+
+### Try These Cool Examples:
+
+**Example 1: Multiple Trigonometric Functions**
+1. Add Expression 1: `sin(x)` (Red)
+2. Add Expression 2: `cos(x)` (Blue)
+3. Add Expression 3: `tan(x)` (Green)
+
+**Example 2: Polar Roses**
+1. Add Expression 1: `r = cos(2*theta)` (Red)
+2. Add Expression 2: `r = cos(3*theta)` (Blue)
+3. Add Expression 3: `r = cos(4*theta)` (Green)
+
+**Example 3: Circles and Parabolas**
+1. Add Expression 1: `x^2 + y^2 = 4` (Red - circle)
+2. Add Expression 2: `y = x^2` (Blue - parabola)
+3. Add Expression 3: `x^2 + y^2 < 9` (Green - filled circle)
+
+**Example 4: Parametric Heart**
+1. Add Expression 1: `(16*sin(t)^3, 13*cos(t) - 5*cos(2*t) - 2*cos(3*t) - cos(4*t))` (Pink ❤️)
+
+**Example 5: Complex Implicit Functions**
+1. Add Expression 1: `(x^2 + y^2 - 1)^3 = x^2*y^3` (Purple - Heart curve)
+2. Add Expression 2: `x^2 - y^2 = 1` (Orange - Hyperbola)
+
+---
+
+## Tips for Best Experience
+
+1. **Use the Grid**: The grid helps visualize coordinates and scale
+2. **Toggle Visibility**: Hide expressions you don't need at the moment
+3. **Color Code**: Use different colors for different types of functions
+4. **Zoom Levels**:
+   - 50-100: Good for most functions
+   - 100-200: Detailed view
+   - 200-500: Very zoomed in
+5. **Multi-line Input**: Use Shift+Enter for longer expressions
+6. **Organize**: Keep similar expressions together in the list
+
+---
+
+## Keyboard Shortcuts (ImGui Default)
+
+- **Tab**: Move between input fields
+- **Shift+Enter**: New line in expression input
+- **Click & Drag**: Interact with sliders
+
+---
+
+Enjoy creating beautiful graphs with your new Desmos-style calculator! 🎉📊✨

src/core/CMakeLists.txt

@@ -23,6 +23,12 @@ endif ()
 
 target_include_directories(${NAME} PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
 target_compile_features(${NAME} PRIVATE cxx_std_20)
+
+# Add /bigobj flag for MSVC to handle large object files
+if(MSVC)
+  target_compile_options(${NAME} PRIVATE /bigobj)
+endif()
+
 target_link_libraries(${NAME}
   PRIVATE project_warnings
   PUBLIC fmt spdlog exprtk SDL2::SDL2 imgui Settings)