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

:root {

    --primary: #1b365d;
    --primary-hover: #264a7f;

    --secondary: #f5f7fa;

    --border: #d9e1ec;

    --success: #1f7a3d;

    --text: #1e293b;

    --shadow:
        0 10px 30px rgba(0,0,0,.08);
}

body {

    background:
        linear-gradient(
            135deg,
            #f8fafc,
            #eef2f7
        );

    font-family:
        "Segoe UI",
        Arial,
        sans-serif;

    color: var(--text);

    min-height: 100vh;

    padding: 30px;
}

.container {

    max-width: 1200px;

    margin: auto;
}

header {

    margin-bottom: 25px;
}

header h1 {

    font-size: 30px;

    font-weight: 600;

    color: var(--primary);

    margin-bottom: 20px;
}

.language-bar {

    display: flex;

    gap: 20px;

    flex-wrap: wrap;
}

.card {

    background: white;

    border-radius: 18px;

    box-shadow: var(--shadow);

    padding: 25px;

    margin-bottom: 25px;
}

.card h2 {

    margin-bottom: 15px;

    color: var(--primary);
}

.form-group {

    margin-bottom: 18px;
}

.form-row {

    display: flex;

    gap: 20px;

    flex-wrap: wrap;
}

label {

    display: block;

    margin-bottom: 8px;

    font-weight: 600;

    color: #475569;
}

input,
select {

    width: 100%;

    height: 44px;

    border: 1px solid var(--border);

    border-radius: 10px;

    padding: 0 12px;

    font-size: 14px;

    transition: .2s;
}

input:focus,
select:focus {

    outline: none;

    border-color: var(--primary);

    box-shadow:
        0 0 0 4px rgba(27,54,93,.10);
}

.phone-wrapper {

    display: flex;

    gap: 10px;
}

.phone-wrapper select {

    width: 140px;
}

.checkbox-row {

    display: flex;

    align-items: center;

    gap: 10px;

    margin-bottom: 20px;
}

.checkbox-row input {

    width: auto;
}

.button-bar {

    display: flex;

    flex-wrap: wrap;

    gap: 12px;

    margin-top: 20px;
}

button {

    border: 0;

    border-radius: 10px;

    padding: 12px 20px;

    font-size: 14px;

    font-weight: 600;

    cursor: pointer;

    transition: .2s;
}

#btnPreview {

    background: #64748b;

    color: white;
}

#btnOutlook {

    background: var(--primary);

    color: white;
}

#btnThunderbird {

    background: var(--success);

    color: white;
}

button:hover {

    transform: translateY(-2px);
}

#btnPreview:hover {

    background: #475569;
}

#btnOutlook:hover {

    background: var(--primary-hover);
}

#btnThunderbird:hover {

    background: #166534;
}

#previewFrame {

    width: 100%;

    height: 650px;

    border: 1px solid var(--border);

    border-radius: 12px;

    background: white;
}

iframe {

    border: 0;

    border-radius: 12px;
}

#mobileContainer {

    transition: .3s;
}

.footer {

    text-align: center;

    padding: 20px;

    color: #64748b;

    font-size: 13px;
}

.badge {

    display: inline-block;

    padding: 5px 10px;

    border-radius: 999px;

    background: #eff6ff;

    color: var(--primary);

    font-size: 12px;

    margin-left: 10px;
}

.dark-preview {

    background: #121212;
}

.dark-preview img {

    filter: invert(1);
}

@media (max-width: 768px) {

    body {

        padding: 15px;
    }

    header h1 {

        font-size: 24px;
    }

    .phone-wrapper {

        flex-direction: column;
    }

    .phone-wrapper select {

        width: 100%;
    }

    .button-bar {

        flex-direction: column;
    }

    button {

        width: 100%;
    }

    #previewFrame {

        height: 800px;
    }
}