app/resources/views/vendor/mail/html/themes/default.css

/* Base */

body,
body *:not(html):not(style):not(br):not(tr):not(code) {
    box-sizing: border-box;
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    position: relative;
}

body {
    -webkit-text-size-adjust: none;
    background-color: #f8fafc;
    color: #475569;
    height: 100%;
    line-height: 1.6;
    margin: 0;
    padding: 0;
    width: 100% !important;
}

p,
ul,
ol,
blockquote {
    line-height: 1.6;
    text-align: left;
}

a {
    color: #3b82f6;
    text-decoration: none;
    font-weight: 500;
}

a img {
    border: none;
}

/* Typography */

h1 {
    color: #1e293b;
    font-size: 22px;
    font-weight: 800;
    margin-top: 0;
    margin-bottom: 24px;
    text-align: left;
    letter-spacing: -0.025em;
}

h2 {
    color: #1e293b;
    font-size: 18px;
    font-weight: 700;
    margin-top: 0;
    text-align: left;
}

h3 {
    color: #1e293b;
    font-size: 16px;
    font-weight: 700;
    margin-top: 0;
    text-align: left;
}

p {
    font-size: 16px;
    line-height: 1.6em;
    margin-top: 0;
    margin-bottom: 16px;
    text-align: left;
}

p.sub {
    font-size: 12px;
}

img {
    max-width: 100%;
}

/* Layout */

.wrapper {
    background-color: #f8fafc;
    margin: 0;
    padding: 0;
    width: 100%;
}

.content {
    margin: 0;
    padding: 0;
    width: 100%;
}

/* Header */

.header {
    padding: 40px 0;
    text-align: center;
}

.header a {
    color: #1e293b;
    font-size: 19px;
    font-weight: 900;
    text-decoration: none;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* Logo */

.logo {
    height: auto;
    max-height: 48px;
    width: auto;
}

/* Body */

.body {
    background-color: #f8fafc;
    margin: 0;
    padding: 0;
    width: 100%;
}

.inner-body {
    background-color: #ffffff;
    border-radius: 24px;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    margin: 0 auto;
    padding: 0;
    width: 570px;
}

.content-cell {
    padding: 48px;
}

/* Buttons */

.action {
    margin: 32px auto;
    text-align: center;
}

.button {
    border-radius: 12px;
    color: #fff !important;
    display: inline-block;
    font-size: 15px;
    font-weight: 700;
    padding: 12px 32px;
    text-decoration: none;
    transition: all 0.2s;
}

.button-primary {
    background-color: #3b82f6;
    box-shadow: 0 10px 15px -3px rgba(59, 130, 246, 0.3);
}

/* Panels */

.panel {
    border-left: #3b82f6 solid 4px;
    margin: 24px 0;
    border-radius: 0 12px 12px 0;
    overflow: hidden;
}

.panel-content {
    background-color: #eff6ff;
    color: #1e40af;
    padding: 20px;
}

/* Footer */

.footer {
    padding: 40px 0;
    text-align: center;
}

.footer p {
    color: #94a3b8;
    font-size: 13px;
    text-align: center;
}

/* Dark Mode Support */
@media (prefers-color-scheme: dark) {
    body, .wrapper, .body {
        background-color: #0f172a !important;
        color: #94a3b8 !important;
    }

    .inner-body {
        background-color: #1e293b !important;
        box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.5) !important;
    }

    h1, h2, h3, .header a {
        color: #f1f5f9 !important;
    }

    p {
        color: #94a3b8 !important;
    }

    .panel-content {
        background-color: #1e293b !important;
        color: #60a5fa !important;
        border: 1px solid #334155 !important;
    }
}