:root {
    --primary-color: #8e44ad;
    --secondary-color: #9b59b6;
    --background-color: #f8f9fa;
    --text-color: #2c3e50;
    --border-color: #e9ecef;
    --shadow-color: rgba(142, 68, 173, 0.1);
    --success-color: #2ecc71;
    --error-color: #e74c3c;
    --card-bg: #ffffff;
    --nav-height: 70px;
    --accent-color: #3498db;
    --gradient-start: #8e44ad;
    --gradient-end: #9b59b6;
}

body.dark-mode {
    --primary-color: #9b59b6;
    --secondary-color: #8e44ad;
    --background-color: #1a1a1a;
    --text-color: #ecf0f1;
    --border-color: #2c3e50;
    --shadow-color: rgba(155, 89, 182, 0.2);
    --card-bg: #2c3e50;
    --accent-color: #3498db;
    --gradient-start: #9b59b6;
    --gradient-end: #8e44ad;
}

[data-theme="ocean"] {
    --primary-color: #3498db;
    --secondary-color: #2980b9;
    --background-color: #ecf0f1;
    --text-color: #2c3e50;
    --border-color: #bdc3c7;
    --card-bg: #ffffff;
    --accent-color: #2ecc71;
    --gradient-start: #3498db;
    --gradient-end: #2980b9;
}

[data-theme="forest"] {
    --primary-color: #2ecc71;
    --secondary-color: #27ae60;
    --background-color: #f1f8e9;
    --text-color: #2c3e50;
    --border-color: #c8e6c9;
    --card-bg: #ffffff;
    --accent-color: #3498db;
    --gradient-start: #2ecc71;
    --gradient-end: #27ae60;
}

[data-theme="sunset"] {
    --primary-color: #e74c3c;
    --secondary-color: #c0392b;
    --background-color: #fff3e0;
    --text-color: #2c3e50;
    --border-color: #ffe0b2;
    --card-bg: #ffffff;
    --accent-color: #f39c12;
    --gradient-start: #e74c3c;
    --gradient-end: #c0392b;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
    min-height: 100vh;
}

.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.top-nav {
    height: var(--nav-height);
    background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
    border-bottom: none;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 2rem;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    box-shadow: 0 2px 4px var(--shadow-color);
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.5rem;
    font-weight: bold;
    color: white;
}

.logo i {
    font-size: 1.8rem;
    color: white;
}

.nav-controls {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.main-content {
    margin-top: var(--nav-height);
    padding: 2rem;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
    width: 100%;
}

.message-form-container {
    background-color: var(--card-bg);
    border-radius: 15px;
    padding: 2rem;
    box-shadow: 0 8px 16px var(--shadow-color);
    margin-bottom: 2rem;
    border: 1px solid var(--border-color);
    background: linear-gradient(135deg, var(--card-bg), var(--background-color));
}

.form-header {
    text-align: center;
    margin-bottom: 2rem;
}

.form-header h2 {
    color: var(--primary-color);
    margin-bottom: 0.5rem;
    font-weight: 600;
    letter-spacing: 0.5px;
    background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.input-wrapper {
    position: relative;
    margin-bottom: 1.5rem;
}

textarea {
    width: 100%;
    height: 150px;
    padding: 1rem;
    border: 2px solid var(--border-color);
    border-radius: 10px;
    background-color: var(--background-color);
    color: var(--text-color);
    font-size: 1rem;
    resize: vertical;
    transition: all 0.3s;
    box-shadow: inset 0 2px 4px var(--shadow-color);
}

textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(44, 62, 80, 0.1);
}

.char-counter {
    position: absolute;
    bottom: 0.5rem;
    right: 1rem;
    font-size: 0.8rem;
    color: var(--secondary-color);
    opacity: 0.7;
}

.form-controls {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.expiry-select {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    background-color: var(--background-color);
    padding: 0.5rem 1rem;
    border-radius: 8px;
    border: 2px solid var(--border-color);
}

.expiry-select i {
    color: var(--primary-color);
}

select {
    padding: 0.5rem;
    border: none;
    background: none;
    color: var(--text-color);
    font-size: 1rem;
    cursor: pointer;
}

.btn {
    padding: 0.8rem 1.5rem;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    transition: all 0.3s;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 8px var(--shadow-color);
}

.btn.primary {
    background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
    color: white;
    font-weight: 500;
    letter-spacing: 0.5px;
    border: none;
}

.btn.primary:hover {
    background: linear-gradient(135deg, var(--gradient-end), var(--gradient-start));
    transform: translateY(-2px);
    box-shadow: 0 4px 12px var(--shadow-color);
}

.btn.secondary {
    background: linear-gradient(135deg, var(--secondary-color), var(--primary-color));
    color: white;
    font-weight: 500;
    letter-spacing: 0.5px;
    border: none;
}

.btn.secondary:hover {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
}

.message-link {
    background: linear-gradient(135deg, var(--card-bg), var(--background-color));
    border-radius: 15px;
    padding: 2rem;
    box-shadow: 0 8px 16px var(--shadow-color);
    border: 1px solid var(--border-color);
}

.link-header {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
}

.link-header i {
    color: var(--primary-color);
    font-size: 1.5rem;
}

.link-header h3 {
    background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    font-weight: 600;
    letter-spacing: 0.5px;
}

.link-box {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.link-box input {
    flex: 1;
    padding: 0.8rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    background-color: var(--background-color);
    color: var(--text-color);
    font-size: 0.9rem;
    letter-spacing: 0.3px;
}

.countdown {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    justify-content: center;
    color: var(--secondary-color);
    font-weight: bold;
    margin-top: 1rem;
}

.countdown i {
    color: var(--primary-color);
}

.theme-switch {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.switch {
    position: relative;
    display: inline-block;
    width: 50px;
    height: 24px;
}

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

.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--secondary-color);
    transition: .4s;
}

.slider:before {
    position: absolute;
    content: "";
    height: 16px;
    width: 16px;
    left: 4px;
    bottom: 4px;
    background-color: white;
    transition: .4s;
}

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

input:checked + .slider:before {
    transform: translateX(26px);
}

.slider.round {
    border-radius: 24px;
}

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

.theme-selector {
    display: flex;
    gap: 0.5rem;
}

.theme-btn {
    width: 40px;
    height: 40px;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    background: linear-gradient(135deg, var(--background-color), var(--card-bg));
    color: var(--text-color);
    transition: all 0.3s;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--border-color);
}

.theme-btn:hover {
    transform: scale(1.1);
    background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
    color: white;
    border-color: transparent;
}

.theme-btn.active {
    background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
    color: white;
    border-color: transparent;
}

@keyframes fadeOut {
    from { opacity: 1; transform: translateY(0); }
    to { opacity: 0; transform: translateY(20px); }
}

.fade-out {
    animation: fadeOut 1s ease-out forwards;
}

@media (max-width: 600px) {
    .top-nav {
        padding: 0 1rem;
    }

    .main-content {
        padding: 1rem;
        margin-top: calc(var(--nav-height) + 1rem);
    }

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

    .expiry-select {
        width: 100%;
        justify-content: center;
    }

    .btn {
        width: 100%;
        justify-content: center;
    }
}