:root {
    /* Color System */
    --color-primary: #E53E3E;
    --color-primary-hover: #C53030;
    --color-secondary: #9B2C2C;
    --color-accent: #F56565;
    --color-success: #38A169;
    --color-warning: #DD6B20;
    --color-error: #E53E3E;
    
    /* Neutral colors */
    --color-black: #0c0c0f;
    --color-gray-900: #171717;
    --color-gray-800: #1f1f1f;
    --color-gray-700: #2d2d2d;
    --color-gray-600: #4b4b4b;
    --color-gray-500: #717171;
    --color-gray-400: #a3a3a3;
    --color-gray-300: #d4d4d4;
    --color-gray-200: #e5e5e5;
    --color-gray-100: #f5f5f5;
    --color-white: #ffffff;
    
    /* Background colors */
    --bg-primary: linear-gradient(135deg, #111, #1a1a1a);
    --bg-card: linear-gradient(to bottom, rgba(32, 32, 36, 0.95), rgba(17, 17, 19, 0.95));
    --bg-input: rgba(12, 12, 14, 0.8);
    --bg-input-focus: rgba(15, 15, 18, 0.9);
    
    /* Text colors */
    --text-primary: var(--color-white);
    --text-secondary: var(--color-gray-300);
    --text-muted: var(--color-gray-400);
    
    /* Border colors */
    --border-color: rgba(255, 255, 255, 0.1);
    --border-focus: var(--color-primary);
    
    /* Shadow */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.5);
    
    /* Animation */
    --transition-fast: 0.15s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
    
    /* Spacing system (8px base) */
    --space-1: 0.25rem;  /* 4px */
    --space-2: 0.5rem;   /* 8px */
    --space-3: 0.75rem;  /* 12px */
    --space-4: 1rem;     /* 16px */
    --space-5: 1.5rem;   /* 24px */
    --space-6: 2rem;     /* 32px */
    --space-8: 3rem;     /* 48px */
    --space-10: 4rem;    /* 64px */
    
    /* Border radius */
    --radius-sm: 0.25rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    
    /* Font sizes */
    --font-size-xs: 0.75rem;    /* 12px */
    --font-size-sm: 0.875rem;   /* 14px */
    --font-size-md: 1rem;       /* 16px */
    --font-size-lg: 1.125rem;   /* 18px */
    --font-size-xl: 1.25rem;    /* 20px */
    --font-size-2xl: 1.5rem;    /* 24px */
    --font-size-3xl: 1.875rem;  /* 30px */
    
    /* Font weights */
    --font-weight-normal: 400;
    --font-weight-medium: 500;
    --font-weight-bold: 600;
}

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

html {
    font-size: 16px;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.5;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--space-4);
}

/* Container */
.app-container {
    width: 100%;
    max-width: 32rem;
    margin: 0 auto;
}

/* Card */
.card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    overflow: hidden;
    position: relative;
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: 0 14px 28px rgba(0, 0, 0, 0.25);
}

.card-header {
    padding: var(--space-6) var(--space-6) var(--space-4);
    text-align: center;
    border-bottom: 1px solid var(--border-color);
}

.card-header h1 {
    color: var(--text-primary);
    font-size: var(--font-size-2xl);
    font-weight: var(--font-weight-bold);
    margin-bottom: var(--space-2);
}

.card-header .subtitle {
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
}

.card-footer {
    padding: var(--space-4) var(--space-6);
    border-top: 1px solid var(--border-color);
    font-size: var(--font-size-xs);
    color: var(--text-muted);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

/* Forms */
form {
    padding: var(--space-6);
}

.form-group {
    margin-bottom: var(--space-5);
}

.form-field {
    position: relative;
}

.form-field label {
    display: block;
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-medium);
    margin-bottom: var(--space-2);
    color: var(--text-secondary);
}

.form-field input {
    width: 100%;
    padding: var(--space-3) var(--space-4);
    font-size: var(--font-size-md);
    background-color: var(--bg-input);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    transition: all var(--transition-fast);
}

.form-field input:focus {
    outline: none;
    background-color: var(--bg-input-focus);
    border-color: var(--border-focus);
    box-shadow: 0 0 0 2px rgba(229, 62, 62, 0.3);
}

.form-field input::placeholder {
    color: var(--color-gray-500);
}

.form-hint {
    margin-top: var(--space-2);
    font-size: var(--font-size-xs);
    color: var(--text-muted);
}

.form-actions {
    margin-top: var(--space-6);
    display: flex;
    justify-content: center;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-3) var(--space-5);
    font-size: var(--font-size-md);
    font-weight: var(--font-weight-medium);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    text-align: center;
    text-decoration: none;
    border: none;
    outline: none;
}

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

.btn-primary:hover, .btn-primary:focus {
    background-color: var(--color-primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(229, 62, 62, 0.4);
}

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

.btn-text {
    margin-right: var(--space-2);
}

.btn-icon {
    display: flex;
    align-items: center;
}

.btn-icon svg {
    width: 16px;
    height: 16px;
}

/* Alerts */
.alert {
    margin-bottom: var(--space-4);
    padding: var(--space-3) var(--space-4);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    animation: slideIn var(--transition-normal);
}

.alert-success {
    background-color: rgba(56, 161, 105, 0.2);
    border-left: 4px solid var(--color-success);
}

.alert-error {
    background-color: rgba(229, 62, 62, 0.2);
    border-left: 4px solid var(--color-error);
}

.alert-icon {
    margin-right: var(--space-3);
    display: flex;
}

.alert-success .alert-icon {
    color: var(--color-success);
}

.alert-error .alert-icon {
    color: var(--color-error);
}

.alert-content {
    flex: 1;
    font-size: var(--font-size-sm);
}

.alert-close {
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text-muted);
    font-size: var(--font-size-xl);
    line-height: 1;
    padding: 0 var(--space-1);
}

/* Theme Switch */
.theme-switch {
    display: flex;
    align-items: center;
}

.theme-switch-label {
    margin-right: var(--space-2);
    font-size: var(--font-size-xs);
}

.switch {
    position: relative;
    display: inline-block;
    width: 40px;
    height: 20px;
}

.switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--color-gray-700);
    transition: var(--transition-normal);
}

.slider:before {
    position: absolute;
    content: "";
    height: 16px;
    width: 16px;
    left: 2px;
    bottom: 2px;
    background-color: white;
    transition: var(--transition-normal);
}

input:checked + .slider {
    background-color: var(--color-primary);
}

input:focus + .slider {
    box-shadow: 0 0 1px var(--color-primary);
}

input:checked + .slider:before {
    transform: translateX(20px);
}

.slider.round {
    border-radius: 34px;
}

.slider.round:before {
    border-radius: 50%;
}

/* Animations */
@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

/* Responsive */
@media (max-width: 576px) {
    .app-container {
        padding: 0;
    }
    
    .card {
        border-radius: 0;
    }
    
    .card-header, .card-footer, form {
        padding: var(--space-4);
    }
    
    .btn {
        width: 100%;
    }
    
    .theme-switch-label {
        display: none;
    }
}

@media (min-width: 577px) and (max-width: 768px) {
    .app-container {
        max-width: 28rem;
    }
}

@media (min-width: 769px) {
    .app-container {
        max-width: 32rem;
    }
    
    .card {
        transform: translateY(0);
        transition: transform var(--transition-normal), box-shadow var(--transition-normal);
    }
    
    .card:hover {
        transform: translateY(-5px);
    }
}