/* Reset and base styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* CSS Variables for theming */
:root {
    --bg-color: white;
    --text-color: #333;
    --container-bg: white;
    --container-border: #e1e5e9;
    --input-bg: white;
    --input-border: #e1e5e9;
    --input-focus-border: #667eea;
    --header-bg: #667eea;
    --button-bg: #667eea;
    --button-hover-bg: #5a67d8;
    --success-bg: #f0fff4;
    --success-border: #38a169;
    --success-text: #22543d;
    --error-bg: #fed7d7;
    --error-border: #e53e3e;
    --error-text: #742a2a;
    --footer-bg: #f8f9fa;
    --footer-text: #666;
    --prefix-bg: #f8f9fa;
    --prefix-text: #666;
    --shadow: rgba(0, 0, 0, 0.1);
}

/* Dark mode variables */
[data-theme="dark"] {
    --bg-color: #1a1a1a;
    --text-color: #e0e0e0;
    --container-bg: #2d2d2d;
    --container-border: #404040;
    --input-bg: #3a3a3a;
    --input-border: #505050;
    --input-focus-border: #667eea;
    --header-bg: #667eea;
    --button-bg: #667eea;
    --button-hover-bg: #5a67d8;
    --success-bg: #1a3d2e;
    --success-border: #38a169;
    --success-text: #9ae6b4;
    --error-bg: #4a1a1a;
    --error-border: #e53e3e;
    --error-text: #feb2b2;
    --footer-bg: #333;
    --footer-text: #ccc;
    --prefix-bg: #404040;
    --prefix-text: #ccc;
    --shadow: rgba(0, 0, 0, 0.3);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background: var(--bg-color);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background-color 0.3s ease, color 0.3s ease;
}

.container {
    max-width: 500px;
    width: 90%;
    background: var(--container-bg);
    border-radius: 20px;
    box-shadow: 0 20px 40px var(--shadow);
    border: 1px solid var(--container-border);
    overflow: hidden;
    position: relative;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

/* Theme toggle */
.theme-toggle {
    position: absolute;
    top: 1rem;
    right: 1rem;
    z-index: 10;
}

.theme-toggle-btn {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: var(--input-bg);
    border: 2px solid var(--input-border);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    transition: all 0.3s ease;
    padding: 0;
}

.theme-toggle-btn:hover {
    transform: scale(1.1);
    border-color: var(--input-focus-border);
}

header {
    background: var(--header-bg);
    color: white;
    padding: 2rem;
    text-align: center;
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
    font-weight: 700;
}

header p {
    font-size: 1.1rem;
    opacity: 0.9;
}

main {
    padding: 2rem;
}

.form-container {
    width: 100%;
}

.form-group {
    margin-bottom: 1.5rem;
}

label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: var(--text-color);
}

input[type="url"],
input[type="text"] {
    width: 100%;
    padding: 0.875rem;
    border: 2px solid var(--input-border);
    border-radius: 10px;
    font-size: 1rem;
    transition: border-color 0.3s ease, box-shadow 0.3s ease, background-color 0.3s ease;
    background: var(--input-bg);
    color: var(--text-color);
}

input[type="url"]:focus,
input[type="text"]:focus {
    outline: none;
    border-color: var(--input-focus-border);
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

input[type="text"]:invalid {
    border-color: var(--error-border);
}

/* Input group styles */
.input-group {
    display: flex;
    width: 100%;
}

.input-group-text {
    background: var(--prefix-bg);
    border: 2px solid var(--input-border);
    border-right: none;
    border-radius: 10px 0 0 10px;
    padding: 0.875rem 1rem;
    font-size: 1rem;
    color: var(--prefix-text);
    white-space: nowrap;
    display: flex;
    align-items: center;
    font-weight: 500;
    transition: border-color 0.3s ease, background-color 0.3s ease;
}

.input-group input[type="text"] {
    border-radius: 0 10px 10px 0;
    border-left: none;
    flex: 1;
}

.input-group input[type="text"]:focus {
    border-left: 2px solid var(--input-focus-border);
}

.input-group:focus-within .input-group-text {
    border-color: var(--input-focus-border);
}

button {
    width: 100%;
    padding: 0.875rem;
    background: var(--button-bg);
    color: white;
    border: none;
    border-radius: 10px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease, background-color 0.3s ease;
    position: relative;
    overflow: hidden;
}

button:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 20px rgba(102, 126, 234, 0.3);
    background: var(--button-hover-bg);
}

button:active {
    transform: translateY(0);
}

button:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

/* Loading state */
.loading {
    display: inline-block;
}

.loading::after {
    content: '';
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 2px solid #ffffff;
    border-radius: 50%;
    border-top-color: transparent;
    animation: spin 1s ease-in-out infinite;
    margin-left: 0.5rem;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Messages */
.message {
    margin-top: 1.5rem;
    padding: 1.5rem;
    border-radius: 10px;
    text-align: center;
    transition: background-color 0.3s ease, border-color 0.3s ease;
}

.message.success {
    background: var(--success-bg);
    border: 2px solid var(--success-border);
    color: var(--success-text);
}

.message.error {
    background: var(--error-bg);
    border: 2px solid var(--error-border);
    color: var(--error-text);
}

.message h3 {
    margin-bottom: 0.5rem;
    font-size: 1.2rem;
}

.message p {
    margin-bottom: 1rem;
}

.short-url-container {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.short-url-container input {
    flex: 1;
    padding: 0.5rem;
    border: 2px solid var(--success-border);
    border-radius: 5px;
    background: var(--input-bg);
    color: var(--success-text);
    font-weight: 600;
}

.short-url-container button {
    width: auto;
    padding: 0.5rem 1rem;
    background: var(--success-border);
    font-size: 0.9rem;
}

.short-url-container button:hover {
    background: #2f855a;
}

/* Utility classes */
.hidden {
    display: none !important;
}

/* Footer */
footer {
    background: var(--footer-bg);
    padding: 1rem;
    text-align: center;
    color: var(--footer-text);
    font-size: 0.9rem;
    transition: background-color 0.3s ease, color 0.3s ease;
}

footer a {
    color: var(--input-focus-border);
    text-decoration: none;
    font-weight: 600;
}

footer a:hover {
    text-decoration: underline;
}

/* Responsive design */
@media (max-width: 600px) {
    .container {
        width: 95%;
        margin: 1rem;
    }
    
    header {
        padding: 1.5rem;
    }
    
    header h1 {
        font-size: 2rem;
    }
    
    main {
        padding: 1.5rem;
    }
    
    .short-url-container {
        flex-direction: column;
    }
    
    .short-url-container button {
        width: 100%;
    }
    
    /* Input group responsive styles */
    .input-group-text {
        padding: 0.875rem 0.5rem;
        font-size: 0.9rem;
    }
}

/* Copy button feedback */
.copy-success {
    background: #38a169 !important;
    transform: scale(0.95);
}

/* Form validation styles */
input:invalid:not(:focus):not(:placeholder-shown) {
    border-color: var(--error-border);
    background: var(--error-bg);
}

input:valid:not(:focus):not(:placeholder-shown) {
    border-color: var(--success-border);
    background: var(--success-bg);
}