:root {
    /* Modern Color Palette */
    --primary-color: #2563eb; /* Royal Blue */
    --primary-hover: #1d4ed8;
    --secondary-color: #64748b; /* Slate Gray */
    --secondary-hover: #475569;
    --bg-color: #f1f5f9; /* Light Slate Background */
    --surface-color: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --danger-color: #ef4444;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    margin: 0;
    padding: 2rem 1rem;
    display: flex;
    justify-content: center;
    min-height: 100vh;
    box-sizing: border-box;
}

.container {
    background: var(--surface-color);
    padding: 2.5rem;
    border-radius: 16px;
    box-shadow: var(--shadow-lg);
    text-align: center;
    max-width: 1000px;
    width: 100%;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

h1 {
    color: var(--text-primary);
    margin: 0;
    font-size: 2rem;
    font-weight: 700;
    letter-spacing: -0.025em;
}

p {
    color: var(--text-secondary);
    margin: 0.5rem 0 1.5rem 0;
    font-size: 1.1rem;
}

/* --- Upload Section --- */
.upload-section {
    border: 2px dashed var(--border-color);
    border-radius: 12px;
    padding: 2rem;
    background-color: #f8fafc;
    transition: all 0.2s ease;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
}

.upload-section:hover {
    border-color: var(--primary-color);
    background-color: #eff6ff;
}

.file-input {
    display: none;
}

#file-name {
    color: var(--text-secondary);
    font-size: 0.9rem;
    font-weight: 500;
}

/* --- Toolbar Styles --- */
.toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background-color: var(--surface-color);
    padding: 0.75rem 1rem;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    flex-wrap: wrap;
    gap: 1rem;
    position: sticky;
    top: 1rem;
    z-index: 50; /* Ensure it stays on top */
}

.mode-group, .settings-group {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.btn-sm {
    padding: 0.5rem 1rem;
    font-size: 0.95rem;
    font-weight: 500;
    background-color: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all 0.2s;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

.btn-sm:hover {
    background-color: #f1f5f9;
    color: var(--text-primary);
    border-color: #cbd5e1;
}

.btn-sm.btn-active {
    background-color: #eff6ff;
    color: var(--primary-color);
    border-color: var(--primary-color);
    font-weight: 600;
}

.settings-group label {
    font-size: 0.9rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.settings-group select {
    padding: 0.4rem 2rem 0.4rem 0.8rem;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    background-color: var(--surface-color);
    color: var(--text-primary);
    cursor: pointer;
    font-size: 0.9rem;
    appearance: none;
    background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 20 20'%3e%3cpath stroke='%236b7280' stroke-linecap='round' stroke-linejoin='round' stroke-width='1.5' d='M6 8l4 4 4-4'/%3e%3c/svg%3e");
    background-position: right 0.5rem center;
    background-repeat: no-repeat;
    background-size: 1.5em 1.5em;
}

.settings-group input[type="color"] {
    width: 36px;
    height: 36px;
    padding: 0;
    border: 2px solid var(--border-color);
    border-radius: 50%;
    overflow: hidden;
    cursor: pointer;
    background: none;
}

.settings-group input[type="color"]::-webkit-color-swatch-wrapper {
    padding: 0;
}
.settings-group input[type="color"]::-webkit-color-swatch {
    border: none;
}

/* --- Canvas Styles --- */
.canvas-wrapper {
    position: relative;
    width: 100%;
    min-height: 400px; 
    border: 2px dashed var(--border-color);
    border-radius: 12px;
    background-color: #f8fafc;
    overflow: auto;
    display: flex;
    justify-content: center;
    align-items: center;
    transform-style: preserve-3d;
    transition: background-color 0.3s, border-color 0.3s;
}

.canvas-wrapper.active {
    border: none;
    background-color: #e2e8f0; /* Darker backdrop for document */
    display: block; 
    text-align: left;
    padding: 2rem; /* Add padding around the PDF page */
}

/* The PDF Render Layer */
#pdf-render {
    display: none; /* Hidden until PDF is loaded */
    position: relative;
    z-index: 1;
    box-shadow: var(--shadow-lg);
    margin: 0 auto;
    background-color: white; /* Simulate paper */
}

/* The Signature Drawing Layer */
#signature-pad {
    display: none; /* Hidden until PDF is loaded */
    position: absolute;
    z-index: 2;
    top: 2rem; /* Match padding of wrapper */
    left: 50%;
    transform: translateX(-50%);
    cursor: crosshair;
    touch-action: none;
}

#placeholder-text {
    color: var(--text-secondary);
    font-size: 1.1rem;
    font-weight: 500;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
}

#placeholder-text::before {
    content: '📄';
    font-size: 3rem;
    opacity: 0.5;
}

/* --- Editable Elements --- */
.text-wrapper {
    position: absolute;
    z-index: 100;
    display: inline-block;
    box-sizing: border-box;
}

.text-content {
    background: transparent;
    border: 1px dashed transparent;
    outline: none;
    padding: 4px 8px;
    font-family: sans-serif;
    min-width: 20px;
    min-height: 1.2em;
    white-space: nowrap;
    cursor: text;
    box-sizing: border-box;
    border-radius: 4px;
}

.text-wrapper .text-content {
    white-space: normal;
    word-break: break-word;
    height: 100%;
    width: 100%;
}

.text-wrapper:hover .text-content,
.text-content:focus {
    border-color: var(--primary-color);
    background-color: rgba(37, 99, 235, 0.05);
}

/* --- Element Toolbar --- */
.element-toolbar {
    position: absolute;
    top: -45px;
    left: 0;
    display: none;
    background-color: var(--text-primary); /* Dark tooltip style */
    border-radius: 6px;
    padding: 4px;
    gap: 4px;
    box-shadow: var(--shadow-md);
    z-index: 101;
    white-space: nowrap;
}

.element-toolbar::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 10px;
    border-width: 5px 5px 0;
    border-style: solid;
    border-color: var(--text-primary) transparent transparent transparent;
}

.toolbar-btn {
    width: 30px;
    height: 30px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 14px;
    border-radius: 4px;
    color: white;
    user-select: none;
    transition: background-color 0.2s;
}

.toolbar-btn:hover {
    background-color: rgba(255, 255, 255, 0.2);
}

.toolbar-btn.delete-btn {
    color: #ffcccc;
}
.toolbar-btn.delete-btn:hover {
    background-color: rgba(220, 53, 69, 0.8);
    color: white;
}

.toolbar-btn.move-btn {
    cursor: grab;
}
.toolbar-btn.move-btn:active {
    cursor: grabbing;
}

/* --- Corner Handles --- */
.corner-handle {
    position: absolute;
    width: 12px;
    height: 12px;
    background-color: white;
    border: 2px solid var(--primary-color);
    display: none;
    z-index: 200;
    box-sizing: border-box;
    border-radius: 50%;
    box-shadow: 0 0 0 2px rgba(255, 255, 255, 0.5);
}

.corner-handle.tl { top: -6px; left: -6px; cursor: nwse-resize; }
.corner-handle.tr { top: -6px; right: -6px; cursor: nesw-resize; }
.corner-handle.bl { bottom: -6px; left: -6px; cursor: nesw-resize; }
.corner-handle.br { bottom: -6px; right: -6px; cursor: nwse-resize; }

.text-wrapper:hover .element-toolbar,
.text-wrapper:focus-within .element-toolbar,
.text-wrapper.selected .element-toolbar,
.text-wrapper:hover .corner-handle,
.text-wrapper:focus-within .corner-handle,
.text-wrapper.selected .corner-handle,
.signature-box:hover .element-toolbar,
.signature-box.selected .element-toolbar,
.signature-box:hover .corner-handle,
.signature-box.selected .corner-handle {
    display: flex;
}

.text-wrapper:hover .corner-handle,
.text-wrapper:focus-within .corner-handle,
.text-wrapper.selected .corner-handle,
.signature-box:hover .corner-handle,
.signature-box.selected .corner-handle {
    display: block;
}

/* --- Signature Box --- */
.signature-box {
    position: absolute;
    z-index: 95;
    display: inline-block;
    border: 1px dashed transparent;
    cursor: grab;
    box-sizing: border-box;
}

.signature-box:hover {
    border: 1px dashed var(--primary-color);
    background-color: rgba(37, 99, 235, 0.05);
}

.signature-box canvas {
    display: block;
    cursor: crosshair;
    touch-action: none;
}

/* --- Controls & Footer --- */
.controls {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
    padding-top: 1rem;
    border-top: 1px solid var(--border-color);
    width: 100%;
}

.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.2s ease;
    font-weight: 600;
    box-shadow: var(--shadow-sm);
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

.btn:active {
    transform: translateY(1px);
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background-color: var(--primary-hover);
    box-shadow: var(--shadow-md);
}

.btn-primary:disabled {
    background-color: #93c5fd;
    cursor: not-allowed;
    box-shadow: none;
    transform: none;
}

.btn-secondary {
    background-color: white;
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background-color: #f8fafc;
    color: var(--text-primary);
    border-color: #cbd5e1;
}

.btn-secondary:disabled {
    background-color: #f1f5f9;
    color: #cbd5e1;
    cursor: not-allowed;
    border-color: #e2e8f0;
}

footer {
    margin-top: 1rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* --- Mobile Responsiveness --- */
@media (max-width: 600px) {
    .container {
        padding: 1rem;
    }

    .toolbar {
        flex-direction: column;
        align-items: stretch;
    }

    .mode-group {
        flex-direction: column;
        width: 100%;
        gap: 0.5rem;
    }

    .settings-group {
        width: 100%;
        justify-content: space-between;
        flex-wrap: wrap;
        margin-top: 0.5rem;
    }
    
    .mode-group button, .settings-group label, .settings-group select {
        flex: 1;
        width: 100%;
    }

    .upload-section {
        width: 100%;
        box-sizing: border-box;
    }

    .controls {
        flex-direction: column;
        gap: 0.5rem;
    }

    .btn, .btn-sm, .upload-section .btn {
        width: 100%;
        justify-content: center;
        box-sizing: border-box;
    }
    

}