:root {
    --bg-color: #f0f2f5;
    --canvas-bg: #ffffff;
    --primary-color: #333333;
    --accent-color: #6366f1; /* Indigo-500 */
    --accent-glow: rgba(99, 102, 241, 0.4);
    --glass-bg: rgba(255, 255, 255, 0.7);
    --glass-border: rgba(255, 255, 255, 0.5);
    --shadow-sm: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --tool-active-bg: rgba(99, 102, 241, 0.1);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Outfit', sans-serif;
    background-color: var(--bg-color);
    background-image: 
        radial-gradient(at 0% 0%, rgba(99, 102, 241, 0.15) 0px, transparent 50%),
        radial-gradient(at 100% 0%, rgba(236, 72, 153, 0.15) 0px, transparent 50%),
        radial-gradient(at 100% 100%, rgba(34, 211, 238, 0.15) 0px, transparent 50%),
        radial-gradient(at 0% 100%, rgba(244, 63, 94, 0.15) 0px, transparent 50%);
    background-attachment: fixed;
    height: 100vh;
    overflow: hidden;
    color: var(--primary-color);
    display: flex;
    justify-content: center;
    align-items: center;
}

#app {
    position: relative;
    width: 100%;
    height: 100%;
}

/* Canvas Styling */
#canvas {
    display: block;
    width: 100%;
    height: 100%;
    background-color: transparent; /* Let body gradient show through slightly or user preference */
    background-color: var(--canvas-bg); /* Clean white canvas */
    cursor: crosshair;
    box-shadow: var(--shadow-sm);
    /* Make canvas feel like a sheet of paper */
    margin: 20px;
    width: calc(100% - 40px);
    height: calc(100% - 40px);
    border-radius: 12px;
    touch-action: none;
}

/* Toolbar Styling */
.toolbar-container {
    position: absolute;
    bottom: 40px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 10;
}

.toolbar {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 24px;
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    border-radius: 20px;
    box-shadow: var(--shadow-lg);
    transition: transform 0.3s ease;
}

.toolbar:hover {
    transform: translateY(-2px);
}

.tool-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    border: none;
    background: transparent;
    cursor: pointer;
    padding: 8px 16px;
    border-radius: 12px;
    color: #64748b;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    overflow: hidden;
}

.tool-btn i {
    font-size: 24px;
    margin-bottom: 4px;
}

.tool-label {
    font-size: 10px;
    font-weight: 500;
    opacity: 0.8;
}

/* Hover & Active States */
.tool-btn:hover {
    background-color: rgba(0, 0, 0, 0.05);
    color: var(--primary-color);
}

.tool-btn.active {
    background-color: var(--tool-active-bg);
    color: var(--accent-color);
    transform: scale(1.05);
}

.tool-btn.active::after {
    content: '';
    position: absolute;
    bottom: -2px;
    width: 20%;
    height: 4px;
    background-color: var(--accent-color);
    border-radius: 2px;
    box-shadow: 0 0 8px var(--accent-glow);
}

/* Specific Action Button (Clear) */
.action-btn {
    color: #ef4444; /* Red for destructive actions */
}

.action-btn:hover {
    background-color: rgba(239, 68, 68, 0.1);
    color: #dc2626;
}

/* Undo/Redo are neutral (non-destructive) actions */
#undo-tool,
#redo-tool {
    color: #475569; /* Slate-600 */
}

#undo-tool:hover,
#redo-tool:hover {
    background-color: rgba(71, 85, 105, 0.1);
    color: #1e293b;
}

.tool-btn:disabled {
    opacity: 0.35;
    cursor: not-allowed;
}

.tool-btn:disabled:hover {
    background-color: transparent;
    color: inherit;
}

.separator {
    width: 1px;
    height: 32px;
    background-color: rgba(0, 0, 0, 0.1);
    margin: 0 4px;
}

/* Responsive adjustments */
@media (max-width: 600px) {
    #canvas {
        margin: 0;
        width: 100%;
        height: 100%;
        border-radius: 0;
    }
    
    .toolbar-container {
        bottom: 20px;
        width: 90%;
    }
    
    .toolbar {
        width: 100%;
        justify-content: space-around;
        padding: 10px;
    }
    
    .tool-label {
        display: none; /* Hide text on small screens */
    }
    
    .tool-btn i {
        font-size: 28px;
        margin-bottom: 0;
    }
}