/* ============================================================
   SIMULASI BELAJAR GRATIS - Stylesheet
   Clean, modern, education-style design
   ============================================================ */

/* ==================== CSS VARIABLES ==================== */
:root {
    /* Primary color palette - educational blue-green theme */
    --color-primary: #2563eb;
    --color-primary-dark: #1d4ed8;
    --color-primary-light: #dbeafe;
    --color-secondary: #10b981;
    --color-secondary-dark: #059669;
    --color-secondary-light: #d1fae5;
    --color-warning: #f59e0b;
    --color-warning-light: #fef3c7;

    /* Neutral colors */
    --color-bg: #f8fafc;
    --color-white: #ffffff;
    --color-text: #1e293b;
    --color-text-light: #64748b;
    --color-border: #e2e8f0;
    --color-disabled: #94a3b8;

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 5rem;

    /* Border radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-full: 50%;

    /* Shadows */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.08);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.12);

    /* Transitions */
    --transition: all 0.3s ease;
}

/* ==================== RESET & BASE ==================== */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
}

a {
    text-decoration: none;
    color: inherit;
}

ul {
    list-style: none;
}

img {
    max-width: 100%;
    display: block;
}

/* ==================== UTILITY CLASSES ==================== */
.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

.section__title {
    font-size: 2rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: var(--spacing-xs);
    color: var(--color-text);
}

.section__subtitle {
    font-size: 1.1rem;
    text-align: center;
    color: var(--color-text-light);
    margin-bottom: var(--spacing-xl);
}

/* ==================== BUTTONS ==================== */
.btn {
    display: inline-block;
    padding: 0.85rem 2rem;
    border-radius: var(--radius-sm);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    border: none;
    text-align: center;
}

.btn--primary {
    background-color: var(--color-primary);
    color: var(--color-white);
    box-shadow: 0 4px 14px rgba(37, 99, 235, 0.3);
}

.btn--primary:hover {
    background-color: var(--color-primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(37, 99, 235, 0.4);
}

.btn--card {
    background-color: var(--color-primary);
    color: var(--color-white);
    padding: 0.7rem 1.5rem;
    font-size: 0.9rem;
}

.btn--card:hover {
    background-color: var(--color-primary-dark);
    transform: translateY(-2px);
}

.btn--disabled {
    background-color: var(--color-disabled);
    color: var(--color-white);
    cursor: not-allowed;
    pointer-events: none;
}

.btn--disabled:hover {
    background-color: var(--color-disabled);
    transform: none;
}

/* ==================== HEADER / NAVIGATION ==================== */
.header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background-color: var(--color-white);
    box-shadow: var(--shadow-sm);
    z-index: 1000;
}

.nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 70px;
    gap: var(--spacing-md);
}

.nav__logo {
    font-size: 1.3rem;
    font-weight: 700;
    color: var(--color-primary);
    white-space: nowrap;
}

.nav__menu {
    display: flex;
    align-items: center;
    gap: var(--spacing-lg);
}

.nav__link {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--color-text-light);
    transition: var(--transition);
}

.nav__link:hover {
    color: var(--color-primary);
}

.nav__donate {
    background-color: var(--color-primary);
    color: var(--color-white);
    padding: 0.6rem 1rem;
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
    font-weight: 600;
    transition: var(--transition);
    white-space: nowrap;
    box-shadow: 0 3px 10px rgba(37, 99, 235, 0.25);
}

.nav__donate:hover {
    background-color: var(--color-primary-dark);
    color: var(--color-white);
    transform: translateY(-2px);
}

/* ==================== HERO SECTION ==================== */
.hero {
    padding-top: 150px;
    padding-bottom: var(--spacing-2xl);
    background: linear-gradient(135deg, var(--color-primary-light) 0%, var(--color-white) 100%);
    text-align: center;
}

.hero__title {
    font-size: 3rem;
    font-weight: 800;
    color: var(--color-text);
    margin-bottom: var(--spacing-sm);
    line-height: 1.2;
}

.hero__subtitle {
    font-size: 1.2rem;
    color: var(--color-text-light);
    margin-bottom: var(--spacing-lg);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

/* ==================== CATEGORY CARDS ==================== */
.categories {
    padding: var(--spacing-2xl) 0;
}

.cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: var(--spacing-lg);
}

.card {
    position: relative;
    background-color: var(--color-white);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    text-align: center;
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
}

.card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-lg);
    border-color: var(--color-primary);
}

.card--development {
    border-color: var(--color-warning-light);
}

.card__badge {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background-color: var(--color-warning-light);
    color: #92400e;
    padding: 0.25rem 0.6rem;
    border-radius: 999px;
    font-size: 0.75rem;
    font-weight: 700;
}

.card__icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-sm);
}

.card__title {
    font-size: 1.3rem;
    font-weight: 700;
    margin-bottom: var(--spacing-xs);
    color: var(--color-text);
}

.card__description {
    font-size: 0.95rem;
    color: var(--color-text-light);
    margin-bottom: var(--spacing-md);
    line-height: 1.7;
}

/* ==================== HOW IT WORKS ==================== */
.how-it-works {
    padding: var(--spacing-2xl) 0;
    background-color: var(--color-white);
}

.steps {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-lg);
}

.step {
    text-align: center;
    padding: var(--spacing-lg);
}

.step__number {
    width: 60px;
    height: 60px;
    border-radius: var(--radius-full);
    background-color: var(--color-primary);
    color: var(--color-white);
    font-size: 1.5rem;
    font-weight: 700;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto var(--spacing-sm);
}

.step__title {
    font-size: 1.15rem;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
    color: var(--color-text);
}

.step__description {
    font-size: 0.95rem;
    color: var(--color-text-light);
}

/* ==================== FEATURES / WHY USE ==================== */
.features {
    padding: var(--spacing-2xl) 0;
}

.features__grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: var(--spacing-lg);
}

.feature {
    background-color: var(--color-white);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    text-align: center;
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
}

.feature:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

.feature__icon {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-sm);
}

.feature__title {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
    color: var(--color-text);
}

.feature__description {
    font-size: 0.9rem;
    color: var(--color-text-light);
    line-height: 1.6;
}

/* ==================== SUPPORT / DONATION SECTION ==================== */
.support {
    padding: var(--spacing-2xl) 0;
    background: linear-gradient(135deg, var(--color-secondary-light) 0%, var(--color-white) 100%);
    text-align: center;
}

.support__content {
    max-width: 760px;
}

.support__title {
    font-size: 2rem;
    font-weight: 800;
    color: var(--color-text);
    margin-bottom: var(--spacing-sm);
}

.support__description {
    font-size: 1.05rem;
    color: var(--color-text-light);
    margin-bottom: var(--spacing-lg);
    line-height: 1.8;
}

/* ==================== FOOTER ==================== */
.footer {
    background-color: var(--color-text);
    color: var(--color-white);
    text-align: center;
    padding: var(--spacing-xl) 0;
}

.footer__title {
    font-size: 1.3rem;
    font-weight: 700;
    margin-bottom: var(--spacing-xs);
}

.footer__subtitle {
    font-size: 0.95rem;
    color: #94a3b8;
    margin-bottom: var(--spacing-sm);
}

.footer__copy {
    font-size: 0.85rem;
    color: #64748b;
}

/* ==================== RESPONSIVE DESIGN ==================== */

/* Tablet */
@media (max-width: 768px) {
    .nav {
        height: 70px;
    }

    .nav__logo {
        font-size: 1.1rem;
    }

    .nav__menu {
        display: none;
    }

    .hero__title {
        font-size: 2.2rem;
    }

    .hero__subtitle {
        font-size: 1rem;
    }

    .section__title,
    .support__title {
        font-size: 1.6rem;
    }

    .cards {
        grid-template-columns: 1fr;
    }

    .steps {
        grid-template-columns: 1fr;
    }

    .features__grid {
        grid-template-columns: 1fr 1fr;
    }
}

/* Mobile */
@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-sm);
    }

    .nav__logo {
        font-size: 0.95rem;
    }

    .nav__donate {
        padding: 0.5rem 0.8rem;
        font-size: 0.85rem;
    }

    .hero {
        padding-top: 120px;
        padding-bottom: var(--spacing-xl);
    }

    .hero__title {
        font-size: 1.8rem;
    }

    .hero__subtitle {
        font-size: 0.95rem;
    }

    .features__grid {
        grid-template-columns: 1fr;
    }

    .btn {
        padding: 0.75rem 1.5rem;
        font-size: 0.9rem;
    }

    .card {
        padding: var(--spacing-lg);
    }

    .card__badge {
        top: 0.8rem;
        right: 0.8rem;
        font-size: 0.7rem;
    }

    .support__description {
        font-size: 0.95rem;
    }
}