/* --- CORE VARIABLES --- */
:root {
    --primary: #6366f1; /* Indigo */
    --primary-light: #e0e7ff;
    --bg: #f3f4f6;
    --white: #ffffff;
    --text: #1f2937;
    --gray: #4b5563;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}

* { box-sizing: border-box; margin: 0; padding: 0; font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif; }

body {
    background-color: var(--bg);
    color: var(--text);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* --- HEADER --- */
header {
    background-color: var(--white);
    padding: 15px 20px;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    width: 100%;
    max-width: 800px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    font-size: 20px;
    font-weight: 900;
    color: var(--primary);
    text-decoration: none;
}

.nav-link {
    text-decoration: none;
    color: var(--text);
    font-weight: 600;
    font-size: 14px;
    margin-left: 20px;
}
.nav-link:hover, .nav-link.active { color: var(--primary); }

/* --- MAIN WRAPPER --- */
.main-wrapper {
    flex: 1;
    padding: 30px 20px;
    width: 100%;
    max-width: 800px;
    margin: 0 auto;
}

/* --- HOME GRID --- */
.dashboard-intro { text-align: center; margin-bottom: 30px; }
.dashboard-intro h1 { font-size: 28px; margin-bottom: 10px; }
.grid-container { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }

.tool-card {
    background: var(--white);
    padding: 30px;
    border-radius: 16px;
    box-shadow: var(--shadow);
    text-align: center;
    text-decoration: none;
    transition: transform 0.2s, box-shadow 0.2s;
    border: 2px solid transparent;
    display: flex;
    flex-direction: column;
    align-items: center;
}
.tool-card:hover { transform: translateY(-3px); border-color: var(--primary); }
.tool-icon { font-size: 48px; margin-bottom: 15px; display: block; }
.tool-title { font-weight: 700; font-size: 18px; color: var(--text); }
.tool-desc { font-size: 14px; color: var(--gray); margin-top: 5px; }

/* --- CALCULATOR PAGES --- */
.calc-container {
    background: var(--white);
    padding: 30px;
    border-radius: 20px;
    box-shadow: var(--shadow);
}

h1.page-title { margin-bottom: 10px; font-size: 26px; color: var(--text); }
p.page-desc { color: var(--gray); margin-bottom: 30px; font-size: 16px; }

/* --- INPUTS --- */
.input-group { margin-bottom: 20px; }
label { display: block; margin-bottom: 8px; font-weight: 600; font-size: 13px; color: var(--gray); text-transform: uppercase; letter-spacing: 0.5px; }

input, select {
    width: 100%;
    padding: 14px;
    border: 2px solid #e5e7eb;
    border-radius: 12px;
    font-size: 16px;
    outline: none;
    background-color: #f9fafb;
    transition: 0.2s;
}
input:focus, select:focus { border-color: var(--primary); background-color: #fff; }

.flex-row { display: flex; gap: 15px; }
.flex-col { flex: 1; }

.btn-calc {
    width: 100%;
    padding: 16px;
    background-color: var(--primary);
    color: white;
    border: none;
    border-radius: 14px;
    font-size: 16px;
    font-weight: 700;
    cursor: pointer;
    margin-top: 10px;
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
}
.btn-calc:hover { background-color: #4f46e5; }

/* --- RESULT BOX --- */
.result-box {
    margin-top: 25px;
    padding: 20px;
    background-color: #eff6ff;
    border-radius: 16px;
    border: 1px solid #bfdbfe;
    display: none;
    color: #1e3a8a;
}
.result-detail { display: flex; justify-content: space-between; padding: 8px 0; border-bottom: 1px solid #dbeafe; }
.result-highlight { font-weight: 800; color: var(--primary); font-size: 24px; display: block; margin-top: 5px; }

/* --- SEO ARTICLE --- */
.seo-article {
    margin-top: 40px;
    padding-top: 30px;
    border-top: 1px solid #e5e7eb;
    line-height: 1.8;
    color: #374151;
}
.seo-article h2 { font-size: 20px; margin-top: 20px; margin-bottom: 10px; color: var(--text); }
.seo-article p { margin-bottom: 15px; }
.seo-article ul { padding-left: 20px; margin-bottom: 15px; }

/* Footer */
footer { text-align: center; padding: 30px; border-top: 1px solid #e5e7eb; margin-top: auto; }
.copyright { font-size: 13px; color: #9ca3af; }

/* Mobile */
@media (max-width: 600px) {
    .grid-container { grid-template-columns: 1fr; }
    .flex-row { flex-direction: column; gap: 15px; }
}